Wastewater treatment process including irradiation of primary solids

ABSTRACT

The present invention provides a method for treating wastewater in which the majority of solids and biological oxygen demand compounds are separated from the wastewater feed using a primary separation process, to produce a solids phase and a water phase. The solids phase is irradiated to reduce the level of pathogens such that it is safe to use as a soil substitute and/or additive so that the solids can thus be disposed of in an environmentally-friendly manner. In additional embodiments, the solids that have been disinfected by radiation are mixed with a suitable inert filler material to produce a soil substitute, fertilizer, compost, or other soil additive. The liquid phase is treated in a substantially smaller system than would be required for treating the full-strength wastewater that can include a suspended media biological regeneration reactor system. The liquid treatment system can include a high flux adsorbent material treatment system integrated with a low flux adsorbent material biological regeneration reactor.

RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 12/832,723 filed on Jul. 8, 2010, which claims the benefit ofU.S. Provisional Patent Application No. 61/224,016 filed on Jul. 8,2009, which are both hereby incorporated by reference in theirentireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a system and method for wastewater treatment.

2. Description of Related Art

Effective handling of domestic sewage and industrial wastewater is anextremely important aspect of increasing the quality of life andconservation of clean water. The problems associated with simplydischarging wastewater in water sources such as rivers, lakes andoceans, the standard practice up until about a half century ago, areapparent—the biological and chemical wastes create hazards to all lifeforms including the spread of infectious diseases and exposure tocarcinogenic chemicals. Therefore, wastewater treatment processes haveevolved into systems ranging from the ubiquitous municipal wastewatertreatment facilities, where sanitary wastewater from domesticpopulations is cleaned, to specialized industrial wastewater treatmentprocesses, where specific pollutants in wastewater from variousindustrial applications must be addressed.

Wastewater treatment facilities typically use multiple treatment stagesincluding preliminary treatment, secondary treatment and tertiarytreatment. Biological oxidation is a well known secondary treatment stepused to remove the majority of the wastewater contaminants. Commonly,effluent from biological oxidation and/or other secondary treatmentprocesses still contains levels of contaminants that requires furthertreatment such as tertiary treatment for their removal.

Biologically refractory and biologically inhibitory organic andinorganic compounds are present in certain industrial and sanitarywastewater streams to be treated. Various attempts have been made toaddress treatment of such biologically refractory and biologicallyinhibitory compounds. Certain types of known treatment include use ofpowdered activated carbon to adsorb and subsequently remove biologicallyrefractory and biologically inhibitory organic compounds.

One portion of certain wastewater treatment processes that isoperationally cost-intensive involves the removal of relatively lowconcentrations of contaminants from wastewater that has been treated byaeration or other secondary processes. While various systems have beenemployed for tertiary treatment, such as adsorption and filters, a needexists for more efficient and lower cost tertiary treatment without thelimitations and disadvantages associated with conventional processes.

SUMMARY OF THE INVENTION

In accordance with one or more embodiments, the invention relates to asystem and method of treating wastewater.

The present invention provides a system and method for treatingwastewater in which the majority of solids and biological oxygen demandcompounds are separated from the wastewater feed using a primaryseparation process, to produce a solids phase and a water phase. Thesolids phase is irradiated to reduce the level of pathogens such that itis safe to use as a soil substitute and/or additive so that the solidscan thus be disposed of in an environmentally-friendly manner. Inadditional embodiments, the solids that have been disinfected byradiation are mixed with a suitable inert filler material to produce asoil substitute, fertilizer, compost, or other soil additive. The liquidphase is treated in a substantially smaller system than would berequired for treating the full-strength wastewater that can include asuspended media biological reactor system. The liquid treatment systemaccording to the present invention includes a high flux adsorbentmaterial treatment system integrated with a low flux adsorbent materialbiological regeneration reactor.

In accordance with one or more embodiments, the invention relates tomethod for treating wastewater that contains solids and biologicaloxygen demand compounds. The process comprises:

separating a majority of the solids and biological oxygen demandcompounds from the wastewater feed using a primary separation process toprovide a solids phase and a water phase including wastewater, and incertain embodiments low concentration wastewater, the solids phasecontaining an initial level of pathogens;

irradiating the solids phase to reduce the level of pathogens;

mixing the wastewater with adsorbent material in a mixing zone for atime sufficient for adsorption of contaminants from the wastewater onthe adsorbent material;

separating and removing a major portion of the wastewater from themixture of wastewater and adsorbent material;

passing the adsorbent material having contaminants adsorbed thereon anda minor portion of the wastewater to a biological regeneration reactor;

retaining the adsorbent material and wastewater in suspension in thebiological regeneration reactor for a period of time that is sufficientto allow microorganisms in the biological regeneration reactor tobiologically act on at least a portion of the adsorbed contaminants;

discharging biologically treated water effluent from the biologicalregeneration reactor; and

recycling regenerated adsorbent material to the mixing zone.

In accordance with one or more embodiments, the invention relates to asystem for treatment wastewater. The system includes a radiationtreatment zone having a source of radiation, an inlet for receivingprimary solids, a solids outlet for discharging irradiated primarysolids and a wastewater outlet. The system also includes a mixing zonehaving a wastewater inlet in communication with the wastewater outlet ofthe radiation treatment zone, an adsorbent material inlet and adischarge outlet. The system further includes an adsorbent materialsettling and liquid separation zone having a slurry inlet incommunication with the discharge outlet of the mixing zone, a treatedwater outlet, and a contaminated adsorbent material outlet. The systemalso includes an adsorbent material biological regeneration reactorsystem having a biological regeneration reactor including a contaminatedadsorbent material inlet in communication with the contaminatedadsorbent material outlet of the adsorbent material settling and liquidseparation zone, a biologically treated water outlet, and a regeneratedadsorbent material outlet in communication with the adsorbent materialinlet of the mixing zone.

In accordance with one or more embodiments, the invention relates to asystem for treatment wastewater. The system includes a radiationtreatment zone having a source of radiation, an inlet for receivingprimary solids, a solids outlet for discharging irradiated primarysolids and a wastewater outlet. The system further includes a high fluxadsorption system and a low flux biological adsorption system. The highflux adsorption system includes an inlet in fluid communication with thewastewater outlet of the radiation treatment zone, a source of adsorbentmaterial for contacting the wastewater and adsorbing contaminants fromthe wastewater, a liquid outlet for discharging a major portion of thereceived wastewater that has been contacted by the adsorbent material,and an adsorbent material outlet for discharging adsorbent materialhaving adsorbed contaminants and a minor portion of the receivedwastewater. The low flux biological adsorption system is for maintainingthe adsorbent material having adsorbed contaminants in suspension for aperiod of time that is sufficient to allow microorganisms to digestadsorbed organic contaminants. The low flux biological adsorption systemincludes a biological regeneration reactor having an inlet for receivingadsorbent material with adsorbed contaminants from the adsorbentmaterial outlet of the high flux adsorption system, a mixed liquoroutlet, and an adsorbent material outlet in communication with thesource of adsorbent material of the high flux adsorption system.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in further detail below and withreference to the attached drawings all of which describe or relate toapparatus, systems and methods of the present invention. In the figures,which are not intended to be drawn to scale, each similar component thatis illustrated in various figures is represented by a like numeral. Inthe figures:

FIG. 1 is a schematic diagram of a membrane biological reactor systemusing a biological reactor which contains one or more zones withadsorbent material in suspension;

FIG. 2 is a schematic diagram of an embodiment of a system for treatmentof wastewater using adsorbent material in a biological reactor upstreamof a membrane operating system used in the present invention toregenerate and/or reactivate adsorbent material;

FIG. 3 is a schematic diagram of a wastewater treatment system includingan embodiment of a high flux adsorbent material treatment system havinga mixing zone and an adsorbent material settling and liquid decantingzone that is integrated with a low flux adsorbent material biologicalregeneration reactor having a biological regeneration reactor and amembrane operating system;

FIG. 4 is a schematic diagram of a wastewater treatment system includinga high flux adsorbent material treatment system having a mixing zone andanother embodiment of an adsorbent material settling and liquidseparation zone that is integrated with a low flux adsorbent materialmembrane biological regeneration reactor;

FIG. 5 is a schematic diagram of a wastewater treatment system includinga high flux adsorbent material treatment system that is integrated withanother embodiment of a low flux adsorbent material biologicalregeneration reactor;

FIG. 6 is a schematic diagram of a wastewater treatment system includinga further embodiment of a high flux adsorbent material treatment systemthat is integrated with a low flux adsorbent material biologicalregeneration reactor;

FIG. 7 is a schematic diagram of a process flow for treating wastewateraccording to one embodiment of the present invention includingirradiation of primary solids; and

FIG. 8 is a schematic diagram of a process flow for treating wastewateraccording to another embodiment of the present invention includingirradiation of primary solids.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, “biologically refractory compounds” refer to those typesof chemical oxygen demand (“COD”) compounds (organic and/or inorganic)in wastewater that are difficult to biologically break down whencontacted with micro-organisms. The “biologically refractory compounds”can have varying degrees of refractory nature, ranging from those thatare mildly refractory to those that are highly refractory.

“Biologically inhibitory compounds” refer to those compounds (organicand/or inorganic) in wastewater that inhibit the biologicaldecomposition process.

“Biologically labile” means easy-to-digest, simple organics such ashuman and animal waste, food waste, and inorganics, such as ammonia andphosphorous-based compounds.

“COD” or “Chemical Oxygen Demand,” refers to a measure of the capacityof the waste to consume oxygen during a chemical reaction that resultsin the oxidation of organic matter and the oxidation of inorganicchemicals such as ammonia and nitrite. COD measurement includesbiologically labile, biologically inhibitory and biologically refractorycompounds.

“BOD₅” refers to biological oxygen demand compounds that arebiologically degradable over a period of 5 days.

“Mixed liquor suspended solids,” or “MLSS,” means microbes and othersubstances, both dissolved and suspended, present in wastewater beingtreated; “mixed liquor volatile suspended solids,” or “MLVSS,” means theactive microbes in the MLSS; and “mixed liquor” means the combinedmixture of wastewater, MLSS and MLVSS.

“Adsorbent” or “adsorbent materials” as used herein means one or more ofgranular activated carbon, including granular activated carbon that hasbeen treated to provide affinity to predetermined chemical species,metals or other compounds found to be present in the wastewater that isto be treated; granular iron-based compounds, e.g., iron oxidecomposites; synthetic resins; and granular alumino-silicate composites.

“Substantially free” or “substantially prevented” in the context ofdescribing the presence of adsorbent material in effluent passing fromone section of a system to another, e.g., from a biological reactorcontaining suspended adsorbent material to a membrane operating system,refers to limiting the amount of adsorbent material passing to themembrane operating system to an amount that does not adversely effectthe requisite efficacy of the membrane filtration process therein. Forinstance, in certain embodiments, “substantially free” or “substantiallyprevented” refers to retaining at least about 80% by volume of thepredetermined amount of adsorbent material to be used in a given systemwithin the biological reactor or one or more biological reaction zones,in further embodiments, at least about 90% by volume and in stillfurther embodiments at least about 95% by volume, and in yet stillfurther embodiments at least about 99% by volume. However, it will beappreciated by one of ordinary skill in the art based upon the teachingsherein that these percentages are merely illustrative, and can varydepending on factors including but not limited to the type ofmembrane(s) used and their resistance to abrasion, the requisiteeffluent quality, the predetermined amount of adsorbent material to beused in a given system, and other factors.

This invention is directed to wastewater treatment systems and methods.“Wastewater” as used herein, for instance, as influent streams 101, 201,301, 401, 501, 601 or 701, defines any water to be treated such assurface water, ground water, and a stream of wastewater from industrial,agricultural and municipal sources, having pollutants of biodegradablematerial, inorganic, labile organic compounds capable of beingdecomposed by bacteria, biologically refractory compounds, and/orbiologically inhibitory compounds, flowing into the wastewater treatmentsystem.

Wastewater from industrial and municipal sources typically containsbiological solids, and inert material and organics, includingbiologically inhibitory and refractory organics. Examples ofbiologically inhibitory and refractory organics may include syntheticorganic chemicals, such as polyelectrolyte treatment chemicals. Otherbiologically inhibitory and refractory organics include polychlorinatedbiphenyls, polycyclic aromatic hydrocarbons, polychlorinateddibenzo-p-dioxin, and polychlorinated dibenzofurans. Endocrinedisrupting compounds are also a class of biologically inhibitory andrefractory organics which can affect hormone systems in organisms andare found in the environment. Examples of endocrine disrupting compoundsinclude: alkylphenolics, such as nonylphenol used for removing oil aswell as natural hormones and synthetic steroids found in contraceptives,such as 17-b-estradiol, estrone, testosterone, ethynyl estradiol.

Other examples of wastewaters to be treated include: high strengthwastewater; low strength wastewater; and leachate from landfills. Watersmay also be treated to remove viruses. Other examples of pollutants inwastewater include: flame retardants, solvents, stabilizers,polychlorinated biphenyls (PCBs); dioxins; furans; polynuclear aromaticcompounds (PNAs); pharmaceuticals, petroleum; petrochemical products;petrochemical byproducts; cellulose; waste products from the pulp andpaper industry, phosphorous; phosphorous compounds and derivatives; andagricultural chemicals such as those derived from or used to producefertilizers, pesticides, and herbicides.

Wastewater from industrial and municipal sources may also contain traceconstituent compounds that originate during the water treatment processand are subsequently difficult to remove. Examples of trace constituentsintroduced during the water treatment process include nitrosamines, suchas N-nitrosodimethylamine (NDMA) which may be released from proprietarycationic and anionic resins.

As used herein, “low concentration wastewater” refers to wastewaterhaving a low concentration of biologically labile (i.e., easy-to-digest)organic compounds, which is lower than the influent feed concentrationthat typically supports a biological treatment system in a conventionalsecondary treatment system such as an activated sludge aerationprocesses or a membrane biological reactor. In addition, as used herein,“low concentration wastewater” includes influents that are not amenableto biological oxidation in a traditional treatment biological system asthe wastewater is too low in strength or contains compounds that are noteasily biologically degraded. They can also contain compounds entirelyresistant to bio-decomposition, biologically inhibitory compounds,and/or biologically refractory compounds, or a combination of these,which either cannot be oxidized biologically, or require much longerresidence times than that which is typically available to a biologicaloxidation system.

In addition, as used herein, “effluent subjected to upstream wastewatertreatment” generally means effluent from one or more conventional or anylater-developed wastewater treatment systems. The “effluent subjected toupstream wastewater treatment” can be derived from wastewater that wassubjected to preliminary and/or primary treatment processes, andsecondary treatment processes, e.g., activated sludge aeration processesor membrane biological reactors, and generally has a low concentrationof biologically labile (i.e., easy-to-digest) organic compounds, whichwould not typically be sufficient to support a biological reaction inmost conventional secondary treatment systems such as activated sludgeaeration processes or membrane biological reactors. In addition, it isalso contemplated in certain embodiments of the present invention that“effluent subjected to upstream wastewater treatment” is effluent thathas also been subjected to one or more conventional or later-developedtertiary treatments. For instance, in certain wastewater treatmentfacilities, effluent from a tertiary treatment system can containcontaminants levels that exceed the mandated discharge levels, and sucheffluent can be treated by the system and method of the presentinvention. In further embodiments, the “effluent subjected to upstreamwastewater treatment” can be derived from a primary separation system inwhich substantially all solids have been removed, such as one or more ofsettlers, clarifiers or other solid separation devices. In still furtherembodiments, “effluent subjected to upstream wastewater treatment” caninclude wastewater that has been subjected to a primary separationsystem followed by irradiation.

In general, wastewater treatment facilities use multiple treatmentstages to clean water so that it may be safely released into bodies ofwater such as lakes, rivers, and streams. Presently, many sanitarysewage treatment plants include a preliminary treatment phase in whichmechanical means are used to remove large objects (e.g., bar screens),and a sand or grit channel where sand, grit and stones settle. Sometreatment systems also include a primary stage where certain fats,greases and oils float to the surface for skimming, and heavier solidssettle to the bottom, and are subsequently treated in an aerobic oranaerobic digester to digest biomass and reduce the levels of biologicalsolids.

After preliminary and/or primary treatment, the wastewater is then sentto a secondary biological activated sludge treatment phase. Biologicaltreatment of wastewater is widely practiced. Wastewater is commonlytreated with waste activated sludge, in which biological solids areacted upon by bacteria within a treatment tank. Activated sludgeprocesses involve aerobic biological treatment in an aeration tank,typically followed by a clarifier/settling tank. Settled sludge isrecycled back to the aeration tank in order to maintain an adequatemixed liquor suspended solids concentration to digest the contaminants.Some alternatives available for disposal of excess bio-solids, e.g.,sludge, include but are not limited to incineration, disposal in alandfill, or use as fertilizer if there are no toxic components.

In the aeration tank, an oxygen-containing gas such as air or pureoxygen is added to the mixed liquor. Oxygen is typically used by thebacteria to biologically oxidize the organic compounds that are eitherdissolved or carried in suspension within the wastewater feed.Biological oxidation is typically the lowest cost oxidation methodavailable to remove organic pollutants and some inorganic compounds,such as ammonia and phosphorous compounds, from wastewater and is themost widely used treatment system for wastewater contaminated withbiologically treatable organic compounds. Wastewaters that containcompounds entirely resistant to bio-decomposition, biologicallyinhibitory compounds, and/or biologically refractory compounds may notbe adequately treated by a conventional simple biological wastewatertreatment system. These compounds can only be acted upon by the bacteriaduring a hydraulic retention time within the specific treatment tank.Because the hydraulic retention time is generally insufficient forbiological oxidation of a sufficient quantity of the biologicallyinhibitory compounds and/or biologically refractory compounds, it islikely that some portion of these recalcitrant compounds may not beadequately treated or destroyed and can pass through a treatment processunchanged or only partially treated prior to discharge in either aneffluent or excess residual sludge.

The mixed liquor effluent from the aeration tank typically enters aclarifier/settling tank where sludge, including concentrated mixedliquor suspended solids, settles by gravity. Settled biomass is wasted,i.e., discharged, to off-site disposal, or circulated back to theaeration tank. However, based on the wastewater and economic needs, somebiological oxidation systems use a different treatment method to removethe solids from the wastewater effluent. The clarifier/settling tank canbe replaced with a membrane operating system, or another unit operationsuch as a dissolved/induced air flotation device. The liquid effluentfrom the clarifier/settling tank, operating system or dissolved/inducedair flotation device is either discharged or given further treatmentprior to discharge. The solids that are removed from theclarification/separation device are returned to the aeration tank asreturn activated sludge in order to retain an adequate concentration ofbacteria in the system. Some portion of this return activated sludge isperiodically removed from this recycle line, known as waste activatedsludge, in order to control the concentration of bacteria in the mixedliquor. This waste activated sludge is then disposed of in apredetermined manor.

One recent advance in conventional industrial biological wastewatertreatment plant technology includes the addition of powdered activatedcarbon particles to the mixed liquor. In biological treatment processesutilizing powdered activated carbon, the organics can be adsorbed ontothe activated carbon and remain within the treatment tank for ahydraulic retention time that is similar to the sludge residence timeand therefore undergo both adsorptive and extended biological treatmentthat result in enhanced removal of certain biologically inhibitory orrefractory compounds. In these processes, certain organic and inorganiccompounds are physically adsorbed to the surface of the powderedactivated carbon particles. At least a portion certain of thesecompounds are then biologically degraded, e.g., oxidized in an aerobicprocess, during the extended time that it is present in the system, andthe remainder is adsorbed and discharged with the activated carbon whenit is wasted from the system.

Powdered activated carbon has been used in conventional biologicaltreatment plants because of its ability to adsorb biologicallyinhibitory and biologically refractory compounds, thereby providing aneffluent with lower concentrations of these pollutants. Inclusion ofpowdered activated carbon in the mixed liquor provides a number ofoperational benefits. The carbon provides the advantages of a suspendedmedia biological treatment system which include increased pollutantremoval and increased tolerance to upset conditions. Additionally, thecarbon allows the biologically inhibitory and biologically refractorycompounds to adsorb onto the surface of the carbon and to be exposed tothe biology for a significantly longer period of time than in aconventional biological treatment system, thereby providing benefitssimilar to that of a fixed film system. The carbon also allows for theevolution of specific strains of bacteria that are more capable ofdigesting the biologically inhibitory organic materials. The fact thatthe carbon is continuously recycled back to the aeration tank with thereturn activated sludge, i.e., the sludge residence time, means that thebacteria can work on digesting the biologically inhibitory organiccompounds adsorbed onto the surface of the carbon for a period of timelonger than the hydraulic detention time of the biological treatmentsystem. This process also results in biological regeneration of thecarbon and allows the carbon to remove significantly more biologicallyinhibitory and biologically refractory compounds than it could in asimple packed bed carbon filter system which would also require frequentreplacement or costly physical regeneration of the carbon once theadsorption capacity of the carbon is exhausted. The carbon in the mixedliquor can also adsorb certain compounds and therefore provide aneffluent that is free of or has a substantially reduced concentration ofcompounds that are not treatable by conventional biological oxidation orotherwise entirely resistant to bio-decomposition. One example of aknown powder activated carbon system is offered by Siemens WaterTechnologies under the trademark “PACT®.”

However, because both biological growth and adsorption of organic andinorganic compounds occurs on the activated carbon in powder form,wasting of excess solids is required. In addition, the powderedactivated carbon is discharged from the treatment process with theremoval of biosolids and must, therefore, be continually replaced. Theprimary mode of contaminant removal in a PACT® system is adsorption,with a secondary function of biological regeneration of organicsadsorbed on the powdered activated carbon; the powdered activated carbonis not retained in the system for a sufficient period of time forbiological regeneration to be the primary treatment mechanism.

Increasingly, sanitary wastewater is being treated using membranebiological reactor technology, which offers improved effluent quality, asmaller physical footprint (more wastewater can be treated per unitarea), increased tolerance to upsets, improved ability to processhard-to-treat wastewaters and a variety of other operational advantages.For example, wastewaters containing high total dissolved solids canexperience settling problems in a conventional clarifier/settling tankand requires significantly more difficult-to-operate solids separationdevices such as a dissolved/induced air flotation device or some othersolids removal system. However, while membrane biological reactorseliminate the settling problems experienced with clarifier/settling tanksystems, they often present problems of membrane fouling and foamingthat do not occur in conventional systems using clarifiers. Membranefouling may be the result of extra-cellular polymeric compounds thatresult from the break-down of the biological life forms in the mixedliquor suspended solids, accumulation of organic materials such as oils,or by scaling caused by inorganic materials.

In addition, to date, membrane biological reactors have not beenutilized commercially with powdered activated carbon addition. There hasbeen some use of powdered activated carbon in surface water treatmentsystems that utilize membranes for filtration. However, it has beenreported that these surface water treatment systems using membranes andpowdered activated carbon have problems with the carbon abrading themembranes and the carbon permanently plugging and/or fouling themembranes.

Industrial wastewater that must be treated prior to discharge or reuseoften include oily wastewaters, which can contain emulsifiedhydrocarbons. Oily wastewaters can come from a variety of industriesincluding steel and aluminum industries, chemical processing industries,automotive industries, laundry industries, and crude oil production andpetroleum refining industries. As discussed above, a certain amount ofnon-emulsified oils and other hydrocarbons may be removed in primarytreatment processes, where floating oils are skimmed from the top.However, biological secondary wastewater processes are generallyemployed to remove the remaining oils from wastewater, typically thedissolved and emulsified oils, though some free oil may exist. Typicalhydrocarbons remaining after primary treatment can include lubricants,cutting fluids, tars, grease, crude oils, diesel oils, gasoline,kerosene, jet fuel, and the like. These hydrocarbons typically must beremoved prior to discharge of the water into the environment or reuse ofthe water in the industrial process. In addition to governmentalregulations and ecological concerns, efficient removal of the remaininghydrocarbons also has benefits, as adequately treated wastewater may beused in many industrial processes and eliminate raw water treatmentcosts and reduce regulatory discharge concerns.

Other types of wastewater that must be treated includes contaminatedprocess water from other industrial processes such as manufacturing ofpharmaceuticals, various goods, agricultural products (e.g.,fertilizers, pesticides, herbicides), and paper processing, as well asmedical wastewater.

Commercial deployment of membrane biological reactors in the treatmentof oily/industrial wastewater has been very slow to develop, mainly dueto maintenance problems associated with oil and chemical fouling of themembranes. Testing of industrial/oily wastewater treated in a membranebiological reactor having powdered activated carbon added to the mixedliquor indicated the same treatment advantages as observed inconventional biological wastewater treatment systems including powderedactivated carbon. It was also noted that the advantages of using amembrane biological reactor can also achieved. A side-by-side comparisonof membrane biological reactors with and without the addition ofpowdered activated carbon demonstrated that the membrane biologicalreactor with powdered activated carbon provided treatment advantages ascompared to the membrane biological reactors without activated carbon.Additionally, the membrane biological reactor without the carbonaddition was very difficult to operate because of dissolved organics andextra cellular polymeric compounds fouling the membranes. However,testing further demonstrated that while the addition of powderedactivated carbon provided a very viable biological wastewater treatmentsystem, the carbon had the deleterious effect of a significant amount ofabrasion to and non-reversible fouling of the membranes. This abrasionand non-reversible fouling was significant enough to result in thissystem being very costly to operate, because of the significantlydecreased life expectancy of the membranes and membrane cleaningfrequency.

Traditional biological oxidation of wastewater is commonly a secondarytreatment step used to remove the majority of the wastewatercontaminants, as it is typically the least costly oxidation methodavailable to treat the organic compounds in the wastewater. In addition,to a lesser extent, a biological system can also remove some inorganiccompounds, as some of the inorganic contaminants that can either beoxidized (e.g., ammonia, phosphates), adhere to the biomass, or can beabsorbed by the biomass. If it is absorbed by the biomass it isultimately discharged with the waste activated sludge.

Notwithstanding the advances and developments in biological oxidationprocesses and other secondary treatments, many secondary treatmentsystems are not capable of adequately treating the wastewater feed bybiological oxidation alone. Wastewater effluent that has been subjectedto secondary treatment sometimes does not have sufficiently low levelsof organic and/or inorganic contaminants to allow discharge or reuse incompliance with regulatory limits. Accordingly, tertiary treatment stepsare often required.

Conventional tertiary treatment steps often include passage of effluentthat has been subject to secondary treatment through one or moreadsorbent columns, including adsorbent material such as activatedcarbon, commonly known as “polishing.” Other tertiary treatmentprocesses can include passing the secondary treatment effluent throughone or more filters, coalescers, UV oxidation, chemical oxidation, othertertiary treatment system, or a combination of these systems. However,these tertiary treatment systems are often large and/or expensive tooperate. A key reason for the problematic size and expense ofconventional tertiary treatment systems is that the entire secondarytreatment effluent having a relatively low concentration ofcontaminants, or a substantial portion thereof, are subject to thesetreatments.

The systems and methods of the present invention obviate the drawbacksof existing tertiary treatment systems, and in certain embodimentsprovide a system that can be used as a secondary or tertiary treatmentsystem, particularly when the wastewater to be treated is a lowconcentration wastewater.

The present invention is directed to an improved wastewater treatmentprocess and system for treating a wastewater stream that has a flow ratesimilar to the influent flow rate, i.e., high flux, in a biologicaltreatment system that has a low flux. This is achieved by adsorbing thecontaminants in the high flux stream onto adsorbent material and thenbiologically regenerating and/or reactivating the adsorbent material ina suspended media membrane biological regeneration reactor system. Thissystem is particularly useful for the processing of low concentrationwastewater that is not particularly suitable for conventional biologicalwastewater treatment because of the low level of biologically labilecompounds.

In certain embodiments, the wastewater treatment process and system forlow contaminant concentration wastewater is useful as a tertiarytreatment system, in which a substantial portion of effluent that hasbeen subjected to secondary treatment and/or other upstream treatment isexposed to a high flux adsorbent material treatment, and a minor portionhaving a relatively higher level of contaminants adsorbed on theadsorbent material is subjected to a low flux adsorbent biologicalregeneration treatment system to regenerate the adsorbent material.

The system and method for treatment of wastewater of the presentinvention comprehends a treatment system which includes a high fluxadsorbent material treatment system integrated with a low flux adsorbentmaterial biological regeneration reactor. In general, the high fluxadsorbent material treatment system includes one or more unit operationsfor mixing low concentration wastewater, or other wastewater containingcompounds entirely resistant to bio-decomposition, biologicallyinhibitory compounds, and/or biologically refractory compounds, or acombination of these, with adsorbent material and decanting liquideffluent having a reduced concentration of contaminants.

The adsorbent material having contaminants from the low concentrationwastewater adsorbed on its surface and/or on the surface of pore wallsis passed to a low flux adsorbent material biological regenerationreactor in which biological micro-organisms degrade organic and certaininorganic contaminants and provide an adsorbent material with lowerconcentrations of these compounds such that it can be reused as a freshadsorbent. In certain embodiments in which the biological reactor is anaerobic biological reactor having a source of oxygen to support aerobicmicro-organisms, the biological reaction includes biological oxidation,wherein organic contaminants in the wastewater are metabolized generallyinto carbon dioxide and water. Excess biomass is removed from theadsorbent material, and the regenerated adsorbent material is recycledto the high flux adsorbent material treatment system. Alternatively, thelow flux adsorbent material biological reactor could be an anaerobicbiological regeneration reactor system, for instance, in embodiments inwhich the compounds to be adsorbed onto the adsorbent material are moreeasily degraded in an anaerobic reactor.

In accordance with one or more embodiments, the present inventionemploys a system including a suspended media membrane biological reactorsystem, such as a granular activated carbon aeration reactor, followedby a membrane operating system, in which adsorbent material issubstantially prevented from entering the membrane operating system, asdescribed in PCT Publication Number WO/09085252, which is incorporatedby reference herein.

In one preferred embodiment, the present invention provides a tertiarytreatment process including the steps of: mixing adsorbent material withlow concentration wastewater; settling the adsorbent material; decantingor otherwise removing the water contacted by the adsorbent material;treating the adsorbent material having adsorbed contaminants in abiological regeneration reactor; treating mixed liquor from thebiological reactor, including mixed liquor suspended solids and mixedvolatile liquor suspended solids, that is substantially free ofadsorbent material, in a membrane operating system; removing excessbiomass from the adsorbent material; and recycling the adsorbentmaterial to the step of mixing it with the low concentration wastewaterin a high flux adsorbent material treatment system. Advantageously, thedecanted supernatant includes a substantial portion of low concentrationwastewater. Accordingly, the biological regeneration reactor and themembrane operating system are employed to treat only a small portion ofthe volume of the total low concentration wastewater effluent previouslysubjected to upstream treatment in prior art processes. A cost-effectivetreatment is thereby provided for low concentration wastewater,especially as compared to conventional tertiary treatment systems suchas granular activated carbon adsorption columns typically utilized forpolishing wastewater discharged from a secondary treatment zone. Thesesystems typically regenerate the adsorbent material with energyintensive regeneration processes such as hot air regeneration or steamregeneration.

The low concentration wastewater treatment system of the presentinvention includes adsorbent material which in certain preferredembodiments is granular activated carbon, in one or more vesselsarranged to adsorb organic compounds in low concentrations. The adsorbedorganics are subsequently exposed to biological micro-organisms in a lowflux adsorbent material biological reactor for a period of time that ismuch longer than the typical hydraulic residence time in granularactivated carbon filters. The low concentration wastewater treatmentsystem and process of the present invention concentrates these organiccompounds from the effluent that has been subjected to upstreamwastewater treatment. Accordingly, when employed as a tertiary treatmentsystem, the low concentration wastewater treatment system and process ofthe present invention allows organic contaminants to be exposed tobacteria for a longer period of time than could normally be achievedbased on the flux of the upstream wastewater treatments in conventionalsecondary treatment systems. Thus, the time for biological reaction, forinstance, biological oxidation in embodiments in which themicro-organisms are aerobic bacteria, is substantially increased. Theuse of biological regeneration rather than the energy intensive systemstypically employed to regenerated granular activated carbon in polishingfilters, is a much more cost effective regeneration system.

In accordance with one or more embodiments, the low concentrationwastewater treatment system of the present invention includes adsorbentmaterial which in certain preferred embodiments is granular activatedcarbon, in one or more vessels arranged to adsorb organic compounds inlow concentrations. The low concentration wastewater treatment systemand process of the present invention concentrates these organiccompounds from the effluent that has been subjected to upstreamwastewater treatment. Accordingly, when employed as a tertiary treatmentsystem, the low concentration wastewater treatment system and process ofthe present invention allows organics to be exposed to bacteria for alonger period of time than could normally be achieved based on the fluxof the upstream wastewater treatments in conventional tertiary treatmentsystems, e.g., carbon polishing systems. Thus, the time for biologicalreaction, for instance, biological oxidation in embodiments in which themicro-organisms are aerobic bacteria, is substantially longer than couldbe achieved in a biological reactor treating the entire influent flow.

In addition, in accordance with one or more embodiments, the lowconcentration wastewater treatment system and process of the presentinvention uses adsorbent material such as granular activated carbon toadsorb the contaminants from the low concentration wastewater, e.g., afull flow low concentration wastewater stream from a secondary treatmentsystem, and transfers the adsorbent material having the adsorbedcontaminants into a relatively small membrane biological reactor systemhaving an arrangement similar to the membrane biological reactor systemdescribed in co-pending and commonly-owned PCT application numberPCT/US10/38644, which is incorporated herein by reference, and in PCTPublication Number WO/09085252, which is also incorporated by referenceherein. The organic compounds that are adsorbed on the adsorbentmaterial are biologically treated in a suspended media membranebiological reactor system, and accordingly obviates the need to treatthe entire wastewater flow and organic load from the upstream wastewatertreatment system. In embodiments in which the suspended media membranebiological reactor system is an aerobic system, the biomass is suppliedwith the requisite oxygen for biological oxidation by using air oroxygen from an air diffuser and/or other source. In embodiments in whichthe suspended media membrane biological reactor system is an anaerobicbiological reactor, the system is operated under requisite conditions toanaerobically degrade the compounds. A relatively small membranebiological reactor system can thus treat the organic compounds that arepresent in low concentrations in the high flux stream of effluentsubjected to upstream wastewater treatment.

In addition, while certain embodiments of the present invention aredescribed as tertiary systems and processes for treating effluent fromone or more upstream wastewater treatment processes, including primaryand/or secondary processes, it will be appreciated by a person ofordinary skill in the art that the systems and methods of the presentinvention can be employed to treat wastewater effluent directly fromcertain processes having low concentrations of organics, for instance,which would not effectively support the biology in a conventionalbiological reactor.

FIGS. 1 and 2 are representations of suspended media membrane biologicalreactor systems suitable for integration with the system of the presentinvention for treating low concentration wastewater, and in particular,for regenerating and/or reactivating adsorbent material havingcontaminants adsorbed thereon in a high flux adsorption step. Thesesystems, described in PCT application number PCT/US10/38644 and in PCTPublication Number WO/09085252, provide for use of adsorbent materialsuch as granular activated carbon in a biological reactor systemupstream of a membrane operating system. In particular, the systemsinclude a separation subsystem that substantially prevents adsorbentmaterial from passing to the membrane operating system and therebyabrading, fouling or otherwise damaging the membranes therein.

Referring now to FIG. 1, a wastewater treatment system 100 isschematically depicted including a biological reactor system 102upstream of a membrane operating system 104. In certain embodiments,biological reactor system 102 includes a single biological reactorvessel. In additional embodiments, biological reactor system 102includes a plurality of biological reactor vessels, one biologicalreactor vessel divided into separate sections, or a plurality ofbiological reactor vessels some or all of which can be divided intoseparate sections. The individual reactor vessels or segregated sectionsare referred to herein generally as a biological reaction zone. Duringwastewater treatment operations using the suspended media membranebiological reactor systems, adsorbent material along withmicro-organisms are maintained in suspension in all of the biologicalreaction zones or a subset of the total number of biological reactionzones. The membrane operating system 104 is maintained substantiallyfree of adsorbent material using one or more of the separationsubsystems described herein. An influent wastewater stream 106 isintroduced from a primary treatment system, a preliminary screeningsystem, or as a direct flow of previously untreated wastewater. Infurther embodiments, the influent wastewater stream 106 can bepreviously treated wastewater, e.g., an effluent from one or moreupstream biological reactors, including, but not limited to, aerobicbiological reactors, anoxic biological reactors, continuous flowreactors, sequencing batch reactors, or any number of other types ofbiological treatment systems capable of biologically degrading organicand in certain embodiments some inorganic compounds.

The biological reactor(s) and/or certain biological reactor zones can bevarious types of biological reactors, including but not limited toaerobic biological reactors, anoxic biological reactors, anaerobicbiological reactors, continuous flow reactors, sequencing batchreactors, trickling filters, or any number of other types of biologicaltreatment systems capable of biologically degrading organic and incertain embodiments some inorganic compounds.

In addition, the biological reactor(s) and/or certain biological reactorzones used herein can be of any size or shape suitable to suspendadsorbent material in conjunction with the suspension system. Forexample, the vessel may have a cross sectional area of any shape, suchas circular, elliptical, square, rectangle, or any irregular shape. Insome embodiments, the vessel can be constructed or modified in order topromote suitable suspension of the adsorbent material.

FIG. 2 schematically depicts the process flow of a wastewater treatmentsystem 200 for producing a treated effluent having reducedconcentrations of biologically labile, biologically refractory,biologically inhibitory and/or organic and inorganic compounds that areentirely resistant to biological decomposition. System 200 generallyincludes a biological reactor 202 and a membrane operating system 204.Biological reactor 202 includes an inlet 206 for receiving wastewaterand an outlet 208 for discharging effluent that has been biologicallytreated, including mixed liquor volatile suspended solids and/or mixedliquor, to the membrane operating system 204.

The biological reactor 202 includes a distributed mass of adsorbentmaterial 234 having pores 236, and an effective amount of one or moremicro-organisms 238, that are both adhered to the adsorbent material andfree-floating and separate from the adsorbent material in the mixedliquor, for acting on biologically labile and certain biologicallyrefractory and/or biologically inhibitory compounds in the mixed liquor.The adsorbent material adsorption sites, including the outer surface ofthe adsorbent granules or particles, and the wall surfaces of pores 236,initially serve as adsorption sites for the biologically labile,biologically refractory, biologically inhibitory and/or organic andinorganic compounds that are entirely resistant to biologicaldecomposition. In addition, micro-organisms 238 can be adsorbed on theadsorption sites of the adsorbent material. This allows for higherdigestion levels of certain biologically refractory and/or biologicallyinhibitory compounds without requiring proportionally longer hydraulicretention times and sludge retention times, due to the fact thosecertain biologically refractory and/or biologically inhibitory compoundsare retained for extended periods of time on the adsorbent material,which are isolated or retained in the biological reactors.

Generally, biologically labile compounds and certain inorganics will bedigested relatively quickly and predominantly by the micro-organismsthat are not adhered to the adsorbent material, i.e., the free-floatingmicro-organisms in the mixed liquor. Certain components includingorganics and inorganics that are entirely resistant to biologicaldecomposition and very refractory biologically refractory andbiologically inhibitory compounds will remain adsorbed on the adsorbentmaterial or can be adsorbed and/or absorbed by free-floating biologicalmaterial in the reactor(s). Ultimately, these non-digestible compoundswill concentrate on the adsorbent to the point where the removal, orwasting, and replacement of the adsorbent will be required to maintainthe quality of effluent at an acceptable level. As the adsorbentmaterial remains in the suspended media membrane biological reactorsystems, micro-organisms grow and are generally retained on theadsorbent material long enough to break down at least a portion ofcertain biologically refractory and/or biologically inhibitory compoundsin the particular influent wastewater, which have been concentrated onthe adsorbent material. While not wishing to be bound by theory, it isbelieved that micro-organisms can eventually evolve into mature strainswith specific acclimation necessary to break down at least a portion ofcertain hard-to-treat compounds in the particular influent wastewater.Over additional time, e.g., several days to several weeks, during whichadsorbent material having certain biologically refractory and/orbiologically inhibitory compounds is maintained in the system, themicro-organisms having a high degree of specificity become second,third, and higher generations, thereby increasing their efficacy tobiodegrade at least a portion of certain of the specific biologicallyrefractory and/or biologically inhibitory compounds that are present inthe particular influent wastewater as the system becomes acclimated.

Various influent wastewaters can be deficient in certain nutrientsbeneficial to the biology that occurs in the biological reactor 202.Further, certain influent wastewaters can have pH levels that areexcessively acidic or caustic. Accordingly, as will be apparent to aperson having ordinary skill in the art, phosphorus, nitrogen, and pHadjustment materials, supplemental simple carbon or chemicals can beadded to maintain optimal nutrient ratios and pH levels for thebiological life and associated activity, including biological oxidation,in the reactor 202.

Effluent from the biological reactor 202 is introduced via a separationsubsystem 222 to an inlet 210 of the membrane operating system 204. Thistransferred mixed liquor, having been treated in biological reactor 202,is substantially free of adsorbent material. In the membrane operatingsystem 204, the wastewater passes through one or more microfiltration orultra-filtration membranes, thereby eliminating or minimizing the needfor clarification and/or tertiary filtration. Membrane permeate, i.e.,liquid that passes through the membranes 240, is discharged from themembrane operating system 204 via an outlet 212. Membrane retentate,i.e., solids from the biological reactor 202 effluent, includingactivated sludge, is returned to the biological reactor 202 via a returnactivated sludge line 214.

Spent adsorbent material from the biological reactor 202, e.g., granularactivated carbon that is no longer effective in adsorbing contaminantssuch as certain compounds entirely resistant to bio-decomposition,biologically refractory compounds and biologically inhibitory compounds,can be removed via a mixed liquor waste discharge port 216 of thebiological reactor 202. A waste outlet 218 can also be connected to thereturn activated sludge line 214 to divert some or all the returnactivated sludge for disposal, for instance, to control theconcentration of the mixed liquor and/or culture. Sludge is dischargedfrom the apparatus with the waste activated sludge when it increases tothe point where the mixed liquor solids concentration is so high that itdisrupts the operation of the particular membrane biological reactorsystem. In addition, the mixed liquor waste discharge port 216 can beused to remove a portion of the adsorbent material, thereby removingsome portion of the biologically refractory compounds, biologicallyinhibitory compounds, and/or organic and inorganic compounds that areentirely resistant to biological decomposition, rather than from thereturn activated sludge line with the waste activated sludge, resultingin a lower concentration of these biologically refractory compounds,biologically inhibitory compounds, and/or organic and inorganiccompounds that are entirely resistant to biological decomposition in thedischarge and a more stable biomass in the membrane biological reactor.An equivalent quantity of fresh or regenerated adsorbent material canthen be added to replace the adsorbent thus removed.

A preliminary screening and/or separation system 220 can be providedupstream of the inlet 206 of the biological reactor 202. Thispreliminary screening and/or separation system can include a dissolvedair floatation system, a coarse screen or a combination of these and/orother preliminary treatment devices for separating suspended matter ofthe type known in the art. Optionally, the preliminary screening and/orseparation system 220 can be eliminated, or other types of preliminarytreatment devices can be included, depending on the particularwastewater being treated.

In order to prevent at least a majority of the adsorbent material 234from entering the membrane operating system 204 and causing undesirableabrasion and/or fouling of the membranes 240, separation subsystem 222is provided. As shown, in FIG. 2, the separation subsystem 222 islocated proximate the outlet of the biological reactor 202. However, incertain embodiments, the separation subsystem 222 can be positioned in aseparate vessel downstream of the biological reactor 202. In eithercase, the separation subsystem 222 includes suitable apparatus and/orstructures for preventing contact between at least a majority of theadsorbent 234 and the membranes 240 in the membrane operating system204. Separation subsystem 222 can comprise one or more of a screeningapparatus, a settling zone, and/or other suitable separation apparatus.

Suitable types of screens or screening apparatus for use in certainembodiments of the suspended media membrane biological reactor systeminclude wedge wire screens, metal or plastic apertured plates, or wovenfabrics, in cylindrical or flat configurations and arranged at variousangles including vertically oriented, horizontally oriented, or at anyangle therebetween. In further embodiments, an active screeningapparatus can be employed such as a rotating drum screen, vibratingscreen or other moving screening apparatus. In general, for systems inwhich the separation subsystem 222 is a screening apparatus, the meshsize is smaller than the bottom limit of the effective granule orparticle size of the adsorbent material that is being used.

Other types of separation subsystems can also be used in the separationsubsystem, as alternatives to, or in combination with, a screeningapparatus. For instance, as further described below, a settling zone canbe provided, in which adsorbent material settles by gravity.

In alternative embodiments, or in conjunction with previously describedembodiments, separation subsystems can include a centrifugal system(e.g., hydrocyclone, centrifuge, or the like), an aerated grit chamber,a floatation system (such as induced gas flotation or dissolved gas), orother known apparatus.

Optionally, or in combination with the separation subsystem 222proximate the outlet of biological reactor 202, a separation subsystemcan be provided between biological reactor 202 and the membraneoperating system 204 (not shown). This alternative or an additionalseparation subsystem can be the same as or different as separationsubsystem 222, in type and/or dimension. For instance, in certainembodiments, a settling zone, a clarifier, a hydrocyclone separator, acentrifuge, or a combination of these can be provided as a distinct unitoperation between biological reactor 202 and membrane operating system204.

Note that the separation subsystem 222 is highly effective forpreventing passage of adsorbent material in its original dimension tothe membrane operating system. In certain preferred embodiments, theseparation subsystem 222 prevents substantially all of the adsorbentmaterial 234 from passage to the membrane operating system 204. However,during operation of the system 200, various causes of attrition of theadsorbent material, including inter-granule collisions, shearing,circulation, or collisions of granules within stationary or movingequipment, can cause particles to be created that are too small to beeffectively retained with the separation subsystem 222. In order tominimize the detriment to the membranes and loss of adsorbent materialto wasting, certain embodiments include a separation subsystem 222 thatis capable of preventing passage of substantially all of the adsorbentmaterial 234 within about 70 to about 80 percent of its originaldimension. The acceptable percentage reduction in the original dimensioncan be determined by a person having ordinary skill in the art, forinstance, based on an economic evaluation. If the reduction in thedimension results in an increase in the particles passing through thescreening system, the membranes will experience increased abrasion.Thus, a cost-benefit analysis can be used to determine what is anacceptable percentage reduction of adsorbent material based on the costof abrasion and eventual replacement of the membranes as compared to thecosts associated with adsorbent material that minimizes breakage, andhandling and operational costs associated with a separation subsystemcapable of preventing passage of particles much smaller than theoriginal adsorbent material granules or particles. In addition, incertain embodiments, some degree of inter-granule collisions, orcollisions of granules within stationary or moving equipment, isdesirable to strip excess biomass from the outer surfaces of theadsorbent material.

Screened or separated mixed liquor effluent from the biological reactor202 can be pumped or flow by gravity (depending on the design of theparticular system) into the membrane operating system 204. In a systemusing an external separation subsystem (not shown), the apparatus ispreferably configured such that adsorbent material separated from themixed liquor passing through an external fine screen or separatorsubsystem falls by gravity back into the biological reactor 202.

Adsorbent material such as granular activated carbon, e.g., suitablypre-wetted to form a slurry of adsorbent material, can be added to thewastewater at various points in the system 200, e.g., from a source 229of adsorbent material. As shown in FIG. 2, adsorbent material can beintroduced at one or more locations 230 a, 230 b, 230 c and/or 230 d.For instance, adsorbent material can be added to the feedstreamdownstream of the preliminary screening system 220 (e.g., location 230a). Optionally, or in combination, adsorbent material can be addeddirectly to the biological reactor 202 (i.e., location 230 b). Incertain embodiments, adsorbent material can be introduced via the returnactivated sludge line 214 (e.g., location 230 c). In additionalembodiments, it can be desirable to add the adsorbent material upstreamof the preliminary screening system 220 (e.g., location 230 d), wherethe preliminary screening system 220 is designed specifically for thisapplication by including screening that allows the adsorbent material topass through and into the biological reactor 202. Mixed liquor passesthrough the separation subsystem 222 and the adsorbent material issubstantially prevented from passing into the membrane operating system204 with the mixed liquor suspended solids.

As the adsorbent material remains in the system and is exposed towastewater constituents including biologically refractory, biologicallyinhibitory compounds and/or organic and inorganic compounds that areentirely resistant to biological decomposition, some or all of theadsorbent material will become ineffective for treating theconstituents, i.e., the adsorption capacity decreases. This will resultin a higher concentration of these constituents entering the membraneoperating system 204, where they pass through the membranes, and aredischarged with the membrane effluent 212. In addition, adsorbentmaterial can become ineffective due to coating with bacteria,polysaccharides and/or extracellular polymeric substances. This layer ofcoating can reach levels where it blocks the pore sites and therebyprevents access for biologically refractory, biologically inhibitoryand/or organic and inorganic compounds that are entirely resistant tobiological decomposition, and consequently prevents adsorption andinhibits biodegradation. In certain embodiments of suspended mediamembrane biological reactor systems, this coating can be removed by ashearing action produced by one or more mechanisms in the system, suchas collisions between adsorbent material granules suspended in the mixedliquor or shearing forces associated with suspension and/or movement ofthe adsorbent material.

When adsorbent material has lost all or a portion of its efficacy forreducing the effluent concentration of biologically refractory,biologically inhibitory and/or organic and inorganic compounds that areentirely resistant to biological decomposition, a portion of theadsorbent material can be wasted via waste port 216, e.g., bydischarging a portion of the mixed liquor containing adsorbent materialdispersed therein.

Additional fresh or regenerated adsorbent material can be introducedinto the system, as described above, via adsorbent material introductionapparatus 229 and/or at one or more suitable addition locations. Theinlet wastewater and the effluent wastewater COD compound concentrationsand/or inorganic compound concentrations, can be monitored to determinewhen the adsorbent material and its accompanying biomass in the systemhave experienced reduced effectiveness. A plot of the difference betweenthe inlet and effluent COD divided by the inlet COD concentration willshow gradual loss of the efficacy of the adsorbent material in the mixedliquor. The same type of plot can be used to monitor the inorganicremoval capacity or the removal of a specific organic species in thesystem. The amount of COD removed from the feed stream can provide anindication of the relative amount of biologically refractory and/orbiologically inhibitory organic compounds that are being removed fromthe wastewater feed. As the operators of the system develop experiencewith treating a particular wastewater, they will be able to determinewhen this ratio indicates a point at which there is a need to remove aportion of the adsorbent material in the biological reactor and replaceit with fresh adsorbent material. The system's required efficiency willthus be regained for the compounds that are biologically refractory,biologically inhibitory and/or entirely resistant to bio-decomposition,for instance, to produce an effluent that is in compliance withregulatory requirements. Sampling and analysis of the effluent forconcentrations of specific organic and inorganic compounds can also beused to determine when efficacy of the adsorbent material and itsaccompanying biomass in the mixed liquor has been reduced and partialreplacement should be initiated.

The operator of a suspended media membrane biological reactor system 200can begin replacing some of the adsorbent material when the effluentconcentrations of specific organic or inorganic compounds start toapproach the facility's permitted discharge concentrations for thesecompounds. The allowed discharge concentrations are typically limited bythe facility's permit, for instance, as determined by the NationalPollutant Discharge Elimination System (NPDES) permit program that isregulated by the United States Environmental Protection Agency, or othersimilar regulating body in a particular state or nation. As operatorsgain experience in operating this system with their particularwastewater, they will be able to anticipate when to commence replacementof adsorbent material. When the operator determines that the efficacy ofthe adsorbent material and its accompanying biomass is approaching aninability to achieve the requisite effluent concentration of pollutants,the normal wasting of excess biomass that is performed by wasting returnactivated sludge from line 218 can cease and the excess biomass and theaccompanying adsorbent material is wasted from the biological reactor202 via waste port 216. The amount of material wasted is determined bywhat is required to maintain the mixed liquor suspended solids withinthe optimum operating range for the particular membrane biologicalreactor system. After replacement of a portion of the adsorbentmaterial, the effluent is monitored by the operator to determine whetherthe requisite contaminant removal efficiency has been restored.Additional replacement can be made as needed based on operatingexperience.

In some embodiments, the system and/or individual apparatus of thesystem can include a controller to monitor and adjust the system asdesired. A controller can direct any of the parameters within the systemdepending upon the desired operating conditions, which may, for example,be based on governmental regulations regarding effluent streams. Thecontroller can adjust or regulate valves, feeders or pumps associatedwith each potential flow based upon one or more signals generated bysensors or timers positioned within the system or individual apparatus.The controller can also adjust or regulate valves, feeders or pumpsassociated with each potential flow based upon one or more signalsgenerated by sensors or timers, which indicate a specific trend, forexample an upward or downward trend in a characteristic or property ofthe system over a predetermined period of time. For example, a sensor inan effluent stream can generate a signal indicating that theconcentration of pollutants such as biologically refractory compounds,biologically inhibitory compounds, and or compounds entirely resistantto bio-decomposition has reached a predetermined value or trend, orindicating that the COD level has reached a predetermined value or trendthereby triggering the controller to perform some act upstream from,downstream from, or at the sensor. This act can include any one or moreof removing adsorbent material from the biological reactor, adding newor regenerated adsorbent material to the biological reactor, adding adifferent type of adsorbent material, adjusting flow of the wastewaterat the feed inlet or inlet to another apparatus within the system,redirecting flow of the feed inlet or inlet to another apparatus withinthe system to a storage tank, adjusting air flow within the biologicalreactor, adjusting residence time within the biological reactor or otherapparatus, and adjusting temperature and/or pH within the biologicalreactor or other apparatus. One or more sensors can be utilized in orwith the one or more apparatus or streams of the system to provide anindication or characteristic of the state or condition of any one ormore processes being performed in the system.

The system and controller of one or more embodiments of the suspendedmedia membrane biological reactor system provide a versatile unit havingmultiple modes of operation, which can respond to multiple inputs toincrease the efficiency of the wastewater treatment system. Thecontroller can be implemented using one or more computer systems whichcan be, for example, a general-purpose computer. Alternatively, thecomputer system can include specially-programmed, special-purposehardware, for example, an application-specific integrated circuit (ASIC)or controllers intended for water treatment systems.

The computer system can include one or more processors typicallyconnected to one or more memory devices, which can comprise, forexample, any one or more of a disk drive memory, a flash memory device,a RAM memory device, or other device for storing data. The memory istypically used for storing programs and data during operation of thesystem. For example, the memory can be used for storing historical datarelating to the parameters over a period of time, as well as operatingdata. Software, including programming code that implements embodimentsof the invention, can be stored on a computer readable and/or writeablenonvolatile recording medium, and then typically copied into memorywherein it can then be executed by one or more processors. Suchprogramming code can be written in any of a plurality of programminglanguages or combinations thereof.

Components of the computer system can be coupled by one or moreinterconnection mechanisms, which can include one or more busses, e.g.,between components that are integrated within a same device, and/or anetwork, e.g., between components that reside on separate discretedevices. The interconnection mechanism typically enables communications,e.g., data, instructions, to be exchanged between components of thesystem.

The computer system can also include one or more input devices, forexample, a keyboard, mouse, trackball, microphone, touch screen, andother man-machine interface devices as well as one or more outputdevices, for example, a printing device, display screen, or speaker. Inaddition, the computer system can contain one or more interfaces thatcan connect the computer system to a communication network, in additionor as an alternative to the network that can be formed by one or more ofthe components of the system.

According to one or more embodiments of the suspended media membranebiological reactor system, the one or more input devices can includesensors for measuring any one or more parameters of system and/orcomponents thereof. Alternatively, one or more of the sensors, pumps, orother components of the system, including metering valves or volumetricfeeders, can be connected to a communication network that is operativelycoupled to the computer system. Any one or more of the above can becoupled to another computer system or component to communicate with thecomputer system over one or more communication networks. Such aconfiguration permits any sensor or signal-generating device to belocated at a significant distance from the computer system and/or allowany sensor to be located at a significant distance from any subsystemand/or the controller, while still providing data therebetween. Suchcommunication mechanisms can be affected by utilizing any suitabletechnique including but not limited to those utilizing wirelessprotocols.

Although the computer system is described by way of example as one typeof computer system upon which various aspects of the suspended mediamembrane biological reactor system and the present invention can bepracticed, it should be appreciated that the invention is not limited tobeing implemented in software, or on the computer system as exemplarilyshown. Indeed, rather than implemented on, for example, a generalpurpose computer system, the controller, or components or subsectionsthereof, can alternatively be implemented as a dedicated system or as adedicated programmable logic controller (PLC) or in a distributedcontrol system. Further, it should be appreciated that one or morefeatures or aspects of the suspended media membrane biological reactorsystem and the present invention can be implemented in software,hardware or firmware, or any combination thereof. For example, one ormore segments of an algorithm executable by a controller can beperformed in separate computers, which in turn, can be in communicationthrough one or more networks.

In some embodiments, one or more sensors can be included at locationsthroughout the system 200, which are in communication with a manualoperator or an automated control system to implement a suitable processmodification in a programmable logic controlled membrane biologicalreactor system. In one embodiment, system 200 includes a controller 205which can be any suitable programmed or dedicated computer system, PLC,or distributed control system. The concentration of certain organicand/or inorganic compounds can be measured at the membrane operatingsystem effluent 212 or the effluent from outlet 208 of the biologicalreactor 202, as indicated by dotted line connections between thecontroller 205 and both the effluent line 212 and the intermediateeffluent line between outlet 208 and inlet 210. In another embodiment,the concentration of volatile organic compounds or other property orcharacteristic of the system can be measured at one or more of inlets201, 206, or 210. Sensors known to those of ordinary skill in the art ofprocess control apparatus can include those based on laser-inducedfluorescence or any other sensor suitable for in situ real timemonitoring of the concentration of organic or inorganic compounds in theeffluent or other property or characteristic of the system. Sensors thatcan be used include submersible sensors for use in oil-in-watermeasurement which use UV fluorescence for detection, such asenviroFlu-HC sensors available from TriOS Optical Sensors (Oldenburg,Germany). The sensors may comprise lenses which are coated or otherwisetreated to prevent or limit the amount of fouling or film that occurs onthe lenses. When one or more sensors in the system generate a signalthat the concentration of one or more organic and/or inorganic compoundsexceeds a predetermined concentration, the control system can implementa responsive action such as a suitable feedback action or feedforwardaction, including but not limited to removing adsorbent material viawaste discharge port 216 (as indicated by dotted line connectionsbetween the controller 205 and the waste discharge port 216); adding newor regenerated adsorbent material via adsorbent material introductionapparatus 229 or at one of the other locations (as indicated by dottedline connections between the controller 205 and the adsorbent materialintroduction apparatus 229); adding a different type of adsorbentmaterial; modifying the hydraulic retention time; modifying thebiological characteristics such as simple carbon food formicro-organisms or adding phosphorus, nitrogen and/or pH adjustmentchemicals; and/or other modifications as described above or that will beapparent to those of ordinary skill in the art.

Note that while the controller 205 and the adsorbent materialintroduction apparatus 229 are shown only with respect to FIG. 2, it isintended that these features and the various feedback and feedforwardcapabilities can be incorporated in any of the systems described herein.In addition, the controller 205 can be electronically connected to othercomponents such as a wastewater feed pump and the suspension system 232.

After the mixed liquor is aerated and treated by the adsorbent materialin the biological reactor 202, the processed mixed liquor passes throughseparation subsystem 222, and is transferred to the membrane operatingsystem 204 substantially free of adsorbent material. The separationsubsystem 222 prevents adsorbent material from passing into the membraneoperating system 204. By maintaining the adsorbent material in thebiological reactor 202, or otherwise upstream of the membrane operatingsystem 204, the suspended media membrane biological reactor systemminimizes or eliminates the likelihood of fouling and/or abrasion of themembrane operating system tank membranes by the adsorbent material.

The membrane operating system 204 contains filtering membranes 240 tofilter the biomass and any other solids in the mixed liquor in themembrane operating system tank 204 from the effluent from the bioreactor212. These membranes 240, which can be in the form of hollow fibermembranes or other suitable configurations, as is known to those ofordinary skill in the art, are typically very expensive and it is highlydesirable to protect them from damage in order to maximize their usefullife. In the suspended media membrane biological reactor system 200, thelife of the membranes in the operating system tank are extended, sincethe separation subsystem 222 substantially reduces or eliminates entryof the adsorbent material such as granular activated carbon, and/or anyother solid granules and particles, into the membrane operating system204.

Outlet 212 transports filtered effluent from the membrane operatingsystem tank 204. Return activated sludge line 214 transports a returnactivated sludge stream from the membrane operating system tank 204 tothe biological reactor 202 for further use in processing of thewastewater feedstream. Excess sludge is wasted from the system usingwaste line 218 as in a conventional membrane biological reactor system.

The suspension system 232 utilizes one or more of jet suspension,mechanical mixing, coarse bubble aeration, gas lift suspension systemssuch as draft tube(s) and draft trough(s), and other types of mechanicalor air suspension systems to maintain the adsorbent material 234 insuspension while minimizing attrition of the adsorbent material 234.

In certain embodiments, after an initial period of time in which theadsorbent material 234 is within the biological reactor 202 and somegranule breakage occurs, e.g., some of the rough and/or protrudingsurfaces of the adsorbent material 234 break off and becomes powder,fines, needles or other smaller particulates, the adsorbent material 234maintained in suspension by the suspension system 232 stabilizes,whereby little or no further breakage or degradation in size occurs.

The concentration of adsorbent material in the mixed liquor is generallydetermined based upon the specific system parameters and wastewater totreat the particular combination of biologically refractory and/orbiologically inhibitory organic or inorganic compounds to meet afacility's discharge requirements. Testing has indicated that operatinga membrane biological reactor with a typical industrial mixed liquorsuspended solids concentration (in a normal range for the particularmembrane biological reactor configuration employed) and an adsorbentmaterial concentration, such as granular activated carbon, of about 20%(of the total mixed liquor suspended solids concentration) was adequateto remove the biologically refractory and/or biologically inhibitoryorganic compounds present in the wastewater feed without creatingfouling problems on the screening system used. Higher concentrations ofadsorbent material can be added to provide an additional margin ofsafety against process upsets that could cause higher than normaleffluent concentrations of biologically refractory compounds,biologically inhibitory compounds, and/or organic or inorganic compoundsentirely resistant to biological decomposition. Note that thisadditional adsorbent material will result in increased screening and/orsettling requirements. The lowest concentration of adsorbent materialthat can be utilized and still achieve the required effluent quality canbe empirically determined, based upon a desired margin of safety againstprocess upsets that is based on experience or otherwise deemedappropriate for the particular system and process.

The suspended media membrane biological reactor systems using adsorbentmaterial upstream of a membrane operating system tank to adsorb organicand inorganic materials (biologically refractory, biologicallyinhibitory or otherwise) as well as to provide for a suspended mediamembrane biological reactor is applicable for a variety of differentconfigurations. In addition, various separation devices may also be usedto maintain the adsorbent material in the biological reactor. It will beappreciated by one of ordinary skill in the art that different systemswill have different economic benefits based on the individualcharacteristics of the wastewater and the region where the facility isto be installed.

The factors that are controlled to produce optimal treatment conditionsinclude the type of adsorbent material, including its size, shape,hardness, specific gravity, settling rate, requisite air flow or othersuspension needs for granule suspension in the mixed liquor, i.e., tomaintain the granular activated carbon as a suspended media, the screenbar spacing or opening size and hole configuration, the concentration ofadsorbent material in the mixed liquor, the concentration of the mixedliquor volatile suspended solids, the total concentration of mixedliquor suspended solids, the ratio of the return activated sludge flowrate divided by the flow rate of the mixed liquor entering the membraneoperating system tank, the hydraulic retention time and the sludgeretention time. This optimization provides adsorption of some portion ofthe biologically refractory compounds, easy to degrade biological oxygendemand compounds (BOD₅), biologically inhibitory compounds, organic orinorganic compounds entirely resistant to biological decomposition, andextra-cellular polymeric substances by the adsorbent material such asgranular activated carbon suspended in the mixed liquor.

Another benefit of the suspended media membrane biological reactorsystem is that sites are provided to which the micro-organisms in themixed liquor suspended solids can adhere. This aspect of the processproduces a mixed liquor volatile suspended solids stream that is morestable and resilient in its response to upset conditions and allowsenhanced biodegradation of the organics present in the wastewater ascompared to a non-granular activated carbon enhanced membrane biologicalreactor operated with similar hydraulic retention times and sludgeretention times. A source of micro-organisms inside the pore spaces, oron the surface, of the adsorbent material serves as a source of seedbacteria in the event of an upstream process upset resulting in the lossof some of the viable micro-organisms floating free in the mixed liquor.In the event of a thermal or toxic chemical shock to the system, whichwould, in conventional systems, terminate certain bacteria, some of themicro-organisms within the pore spaces or on the surface can survive,thus only a fraction of the recovery time is necessary as compared toconventional systems without adsorbent. For instance, in systems wherethe bacteria is mesophilic, the adsorbent can allow some bacteria withinthe pore sites to survive in the event of thermal shock due to increasedtemperature. Likewise, in systems where the bacteria is thermophilic,the adsorbent allows some bacteria within the pore sites to survive inthe event of thermal shock due to decreased temperature. In both ofthese circumstances, the time required for the cultures to re-acclimatecan be greatly reduced. In addition, in the event of a system shock thatterminates all or a portion of the micro-organism population, thepresence of adsorbent material allows for continued operation, in whichlabile, refractory, and inhibitory contaminants can be adsorbed whilethe micro-organism population is adjusted.

The various benefits have been shown to result in a more rapidacclimation of the mixed liquor to the wastewater feed, reduce foulingof the membranes, an improved tolerance to variations in feedconcentrations and flow rate, produce a sludge that can be dewateredmore quickly with a less oily nature that is easier to handle, and aneffluent having a lower concentration of organic and inorganicimpurities than can be obtained from a conventional membrane biologicalreactor apparatus.

The use of an adsorbent such as granular activated carbon in place ofpowdered activated carbon allows the elimination of the membrane foulingand/or abrasion that have been identified as a problem in powderedactivated carbon membrane biological reactors testing.

Although the use of granular activated carbon in place of powderedactivated carbon does not use carbon as efficiently on a weight basis,the suspended media membrane biological reactor system and a separationsubsystem substantially prevents the granular activated carbon fromentering the membrane operating system thereby minimizing or eliminatingthe likelihood of abrasion and fouling of the membranes. The impact ofthe reduced adsorption efficiency as a result of using granularactivated carbon in place of powdered activated carbon does not,however, significantly impact the efficacy of the overall activatedcarbon-enhanced membrane biological reactor apparatus.

Testing has indicated that the principal mechanism of removal of certainbiologically inhibitory organics and/or biologically refractorycompounds is related to an increase in the residence time that thebiologically refractory and biologically inhibitory compounds areexposed to the micro-organisms in the powdered activated carbon enhancedapparatus. Micro-organisms in the mixed liquor volatile suspended solidsadsorbed on the adsorbent material such as granular activated carbonhave a longer period of time to digest these certain biologicallyrefractory and biologically inhibitory compounds. Increased residencetime for biodegradation has been shown to be a major factor in reducingthe concentration of certain biologically refractory and biologicallyinhibitory compounds in the membrane biological reactor effluent, andthe higher adsorption efficiency of the powdered activated carbon is notrequired to achieve the desired results.

Granular activated carbon in a carbon-assisted membrane biologicalreactor performs as well or better than a powdered activated carbonenhanced membrane biological reactor in enhancing the removal ofbiologically refractory compounds, biologically inhibitory compounds,compounds that are entirely resistant to biological decomposition, andextra-cellular polymeric compounds by allowing for substantialregeneration of the granular activated carbon. Also, because of itslarger size, it can be effectively filtered or otherwise separated fromthe mixed liquor that enters the membrane operating system tank(s). Theabrasion that occurs when using the powdered activated carbon can beeliminated or significantly reduced by employing granular activatedcarbon in the suspended medial membrane biological reactor system.

While the use of the powdered activated carbon particles in a membranebiological reactor has demonstrated some of the same advantagesdescribed above for the granular activated carbon system, the observedmembrane abrasion from the powdered activated carbon particles in themembrane operating system tank(s) is unacceptable since the membrane'suseful life can be reduced to an unacceptable level, e.g., significantlyless than a typical life expectancy of a membrane. Since the cost of themembranes represents a significant portion of the total cost of amembrane biological reactor system, an extension of their useful life isan important factor in the operating cost of the membrane operatingsystem.

FIGS. 3-6 depict certain embodiments of the wastewater treatment systemof the present invention. As noted above, the wastewater treatmentsystem of the present invention can employ a suspended media membranebiological reactor system described with reference to FIGS. 1 and 2 andalso described in PCT application number PCT/US10/38644 and PublicationNumber WO/09085252. While certain preferred embodiments are described inconjunction with treatment of low concentration wastewater, e.g.,derived from effluent subjected to upstream wastewater treatment, itwill be appreciated by one having ordinary skill in the art, having thebenefit of the present disclosure, that the wastewater treatment systemof the present invention can advantageously be employed to treatwastewater having some level of biologically labile compounds as well ascompounds entirely resistant to bio-decomposition, biologicallyinhibitory compounds, and/or biologically refractory compounds, or acombination of these.

Referring to FIG. 3, a treatment system 354 is schematically shown fortreating effluent 351 from one or more upstream wastewater treatmentstages, collectively identified as wastewater treatment system 350.Wastewater treatment system 350 typically treats an influent 301 anddischarges excess activated sludge 352 and a liquid treated effluent 351that is referred to herein as “low concentration wastewater” or“effluent subjected to upstream wastewater treatment”, as isconventionally known. While the description which follows refers toeffluent 351 as being derived from one or more upstream wastewatertreatment stages, e.g., primary and/or secondary, it will be understoodby one of ordinary skill in the art that the systems and methods of thepresent invention are also effective for treating low concentrationwastewater from other sources, such as directly from a process havinglow levels of suspended solids and relatively low levels of dissolvedorganics. In addition, the wastewater treatment system of the presentinvention can advantageously be employed to treat wastewater having somelevel of biologically labile compounds as well as compounds entirelyresistant to bio-decomposition, biologically inhibitory compounds,and/or biologically refractory compounds, or a combination of these. Inthese embodiments, stream 351 can be a direct influent, or subject tominimal upstream processing, such as a primary separation system inwhich substantially all solids have been removed.

As discussed above, tertiary treatment of an effluent from a secondarytreatment zone commonly includes passing the entire secondary effluentthrough one or more granular activated carbon columns or other tertiarysystem for additional treatment, e.g., polishing, in order to achievethe required water quality standards. In contrast, treatment system 354of the present invention, which can be used as a tertiary treatmentsystem, employs a combination of a high flux adsorbent material system359 to adsorb a substantial amount of contaminants, and a further system399 for biologically treating adsorbed contaminants, i.e., contaminantsadsorbed on the adsorbent material, by biological regeneration and/orreactivation.

In general terms, the treatment system 354 of the present inventioncomprehends a high flux adsorbent material treatment system 359 and alow flux adsorbent material biological regeneration reactor system 399.The high flux adsorbent material treatment system 359 includes a mixingzone 360 for receiving fresh and/or recycled adsorbent material, e.g.,from a source 393 of adsorbent material. Mixing zone 360 is in fluidcommunication with a source of low concentration wastewater 351 such aseffluent subjected to upstream wastewater treatment or other lowconcentration wastewater. Mixing zone 360 intimately mixes the adsorbentmaterial and wastewater, and passes the mixture of low concentrationwastewater and adsorbent material 361 to an adsorbent material settlingand liquid separation zone 370. A major portion of the overall liquidvolume/flux is decanted or otherwise discharged from the adsorbentmaterial settling and liquid separation zone 370 as effluent 371, whichcan optionally be subject to further tertiary treatment 390. Theadsorbent material is removed from the adsorbent material settling andliquid separation zone 370 as an adsorbent material effluent discharge372 which is passed to the low flux adsorbent material biologicalregeneration reactor system 399, which includes a biologicalregeneration reactor 302, a membrane operating system 304, an adsorbentmaterial shearing zone 386 and an adsorbent material/biomass separationzone 387. In aerobic systems, the biological regeneration reactor 302further includes a source of oxygen, and micro-organisms biologicallyoxidize organics and certain inorganics adsorbed on the adsorbentmaterial in the biological regeneration reactor 302, and mixed liquorincluding mixed liquor volatile suspended solids is passed through anadsorbent solids separation apparatus 322 and discharged as biologicalregeneration reactor mixed liquor effluent 308 outlet to a solidsseparation apparatus to remove biomass and any other solids in the mixedliquor. For example, in certain embodiments of the present invention,the solids separation apparatus includes membrane operating system 304,in which the biological regeneration reactor effluent 308 is passed toan inlet 310 of the membrane operating system 304 to remove biomass andany other solids in the mixed liquor. Membrane-treated effluent 312 isdischarged as permeate, and activated sludge 314, as retentate, isreturned to the biological regeneration reactor 302. A portion of theactivated sludge can be discharged from the system via a waste line 318.Adsorbent material from the biological regeneration reactor 302 ispassed to the adsorbent material shearing zone 386, in which excessbiomass is sheared from the granules or particles of adsorbent material.Biomass is separated from the adsorbent material in the adsorbentmaterial/biomass separation zone 387. Separated adsorbent material thathas been regenerated via biological regeneration reactor 302 andsubsequently sheared and separated in zones 386 and 387 is recycled viarecycle line 389 to the mixing zone 360, and biomass is returned via 388to the biological regeneration reactor 302. Spent adsorbent material canbe removed from the biological regeneration reactor 302, via line 316,or from the adsorbent material/biomass separation zone 387 via line 392.

In certain embodiments, the functions of the adsorbent material shearingzone 386 and an adsorbent material/biomass separation zone 387 can beintegrated in a single unit operation. Examples of apparatus that canperform shearing and biomass separation include continuous backwashfilters and/or walnut shell filter. In additional embodiments, some orall of the functionality of the adsorbent material shearing zone 386 andan adsorbent material/biomass separation zone 387 can be accomplished inthe biological regeneration reactor 302, for instance if biologicalregeneration reactor 302 is suitably equipped with sufficient turbulenceto promote the necessary shearing. In these embodiments, the biomass canremain in the biological regeneration reactor 302, and the regenerated,sheared and separated adsorbent material can be passed directly to themixing zone 360.

In addition, adsorbent material can be introduced at various locationsin the system. For instance, a source 393 can be used to introduce freshor regenerated adsorbent material via line 389, e.g., mixed withrecycled adsorbent material that is returned to mixing zone 360. Othersuitable locations can be used for introducing adsorbent material, forinstance, as discussed in with reference to FIG. 2, directly into mixingzone 360, or directly into liquid separation zone 370.

In certain embodiments, the adsorbent material effluent stream 372 islacking in sufficient nutrients to support the biology within biologicalregeneration reactor 302. Accordingly, a portion of the raw wastewaterfrom influent 301 can be introduced into the biological regenerationreactor 302, for instance via a bypass stream 303. This stream 303 canbe intermittent, or continuous, depending on the type of wastewater, itsconstituents, and whether or not the wastewater composition changes overtime. Adding this raw wastewater or some other simple carbon source canenhance the development of bacteria that is required for optimaldegradation of refractory organics that are removed from lowconcentration wastewater stream 351 by the adsorbent material. The rawwastewater initially provides bacteria that become acclimated to the rawwastewater feed constituents, and these bacteria then provide a startingpoint for bacteria that can biologically degrade the refractoryorganics. The initial bacteria can evolve over time into species thatcan digest the refractory organics. Having an untreated wastewaterstream feeding the organisms in biological regeneration reactor 302 willresult in a bacteria population that is capable of digesting morecomplex organic compounds than the bacterial that would be present in asanitary wastewater treatment system, which is generally the most commonstarting point for bacteria in a wastewater treatment system.Alternatively, or in combination, seed cultures can be added to thebiological regeneration reactor 302. Periodically, additional seedculture of the same or a different type can be added, for instance, ifthe bacteria population decreases due to an upstream event or thermalshock, or if the wastewater contaminants change.

Influent low concentration wastewaters can be deficient in certainnutrients beneficial to the biology that occurs in the biologicalregeneration reactor 302. Further, certain influent wastewaters have pHlevels that are excessively acidic or caustic. Accordingly, as will beapparent to a person having ordinary skill in the art, phosphorus,nitrogen, and pH adjustment chemicals can be added to maintain optimalnutrient ratios and pH levels for the biological life and associatedactivity, including biological oxidation, in the biological regenerationreactor 302. Additionally, in certain embodiments, a stream of simplecarbon compounds can be added to increase the rate of biodegradation ofthe adsorbed contaminants.

In particular, low concentration wastewater is introduced to the mixingzone 360, which is supplied with adsorbent material, such as granularactivated carbon. The adsorbent material can include fresh adsorbentmaterial and/or adsorbent material recycled from within the system,i.e., from the adsorbent material/biomass separation zone 387. The lowconcentration wastewater and adsorbent material is intimately mixed inmixing zone 360, and at least a portion of the dissolved organics and/orinorganics which were present in effluent 351 are adsorbed on theadsorbent material, i.e., on the outer surface, on the pore wallsurfaces, or both.

A mixed stream 361 from the mixing zone 360, including adsorbentmaterial that has adsorbed at least a portion of the organics and/orinorganics from the effluent 351, is then passed to the adsorbentmaterial settling and liquid separation zone 370, e.g., in the form of aslurry. If organics and/or inorganics remain in the liquid portion ofthe mixture 361, adsorption can continue in the adsorbent materialsettling and liquid separation zone 370, depending on the flow rate,settling rate, adsorptive capacity of the adsorptive material, and otherfactors. Preferably, a substantial amount of contaminants are removed sothat the remaining liquid portion, decanted or otherwise removed as ahigh flux adsorbent material effluent stream 371, at least meets levelsmandated by the relevant regulatory bodies, and can be recycled ordischarged in an environmentally friendly manner. If necessary, stream371 can be passed to a tertiary treatment zone 390 for final polishing,and the polished effluent 391 discharged. Advantageously, the organicsand/or inorganics removed from stream 371 (i.e., as compared to theeffluent 351 from wastewater treatment system 350) are adsorbed on theadsorbent material, and stream 371 represents a major portion of theliquid volume of the initial low concentration wastewater streampresented to system 354, e.g., stream 351. In certain embodiments, theflux of stream 371 is at least 90% of the flux of stream 351; in otherembodiments, the flux of stream 371 is at least 95% of the flux ofstream 351; in additional embodiments, the flux of stream 371 is atleast 99% of the flux of stream 351; in further embodiments, the flux ofstream 371 is at least 99.9% of the flux of stream 351; and in stillfurther embodiments, the flux of stream 371 is at least 99.99% of theflux of stream 351. The proportion of stream 371 relative to stream 351can depend on various factors, including the level of initialcontamination, the degree of mixing in the mixing zone 360, the volume,configuration and residence time within the adsorbent material settlingand liquid separation zone 370, the adsorptive capacity of the adsorbentmaterial, and/or other factors.

In one embodiment, the adsorbent material settling and liquid separationzone 370 includes a vessel configured with an inverse conical orfrusto-conical bottom portion 385. Accordingly, adsorbent material isremoved by gravity settling through a discharge port at the bottom ofthe vessel, along with a minor portion of water from the influent stream351. In addition, in embodiments in which organics and/or inorganics arenot sufficiently adsorbed in the mixing zone 360, the adsorbent materialsettling and liquid separation zone 370 can be suitably dimensioned toprovide additional contact time between the thus-treated wastewatereffluent and the adsorbent material. In certain embodiments of theadsorbent material settling and liquid separation zone 370, this can beaccomplished with a vessel providing a low concentration wastewaterresidence time of greater than about 5 minutes, and in certainembodiments having a residence time of greater than about 15 minutes. Ofcourse, one of ordinary skill in the art, having the benefit of theteachings herein, will appreciate that the time required to separate theadsorbent from the effluent will depend on a variety of factors,including but not limited to the density of the adsorbent material, thedensity of the wastewater, and the geometry of the tank.

The adsorbent material settling and liquid separation zone 370 canpreferably include a separation subsystem for preventing adsorbentmaterial from exiting the adsorbent material settling and liquiddecanting zone with the high flow of liquid effluent 371. In certainembodiments, the separation subsystem can comprise a quiescent zone 384,e.g., formed by baffles 381 and 382. This permits a substantial amountof the adsorbent material present in the adsorbent material settling andliquid separation zone 370 to be directed towards the inverse conical orfrusto-conical bottom portion 385. In additional embodiments, theseparation subsystem can comprise a screening apparatus 383 proximatethe outlet of the adsorbent material settling and liquid separation zone370. The screening apparatus 383 can be a stationary screen, a movingscreen, a wedge wire screen, a rotary drum screen, or other suitablescreen type. In further embodiments, the separation subsystem cancomprise both the quiescent zone 384 and the screening apparatus 383. Instill further embodiments, the separation subsystem can include aquiescent zone and a weir located at the liquid effluent 371 outlet ofthe adsorbent material settling and liquid separation zone 370. Notethat the separation subsystem used in the adsorbent material settlingand liquid decanting zone 370 can be the same or different than theseparation subsystem used in biological regeneration reactor 302including one or more of a screening system, a settling zone, or acombination thereof. In addition, if further solids removal from theeffluent 371 is required, a clarifier, filter, or other separationdevice can be included in fluid communication downstream of the effluent371 outlet of the adsorbent material settling and liquid separation zone370.

For instance, the separation subsystem within the adsorbent materialsettling and liquid separation zone 370 can be eliminated in embodimentsin which the adsorbent material has a relatively high specific gravity(e.g., greater than about 1.10 in water at 20° C., in certainembodiments greater than about 1.40 in water at 20° C., and inadditional embodiments having a specific gravity of up to about 2.65 inwater at 20° C.), whereby high settling rates, in combination withsuitable dimensions and configurations of the adsorbent materialsettling and liquid decanting zone 370, including the geometry of thebottom portion 385 and the position of the effluent 371 outlet. In theseembodiments, a clarifier, filter, or other separation device can beprovided downstream of the adsorbent material settling and liquidseparation zone 370. Alternatively, a clarifier, filter, or otherseparation device can also be eliminated in embodiments in which theeffluent 371 is subjected to a final polishing apparatus 390. In certainembodiments, if the final polishing apparatus 390 is a fixed bedgranular activated carbon adsorption column, any excess adsorbentmaterial from the adsorbent material settling and liquid decanting zone370 that may pass with effluent 371 will not impact the final effluentas it will be trapped in the polishing apparatus 390.

Adsorbent material passes from the adsorbent material settling andliquid separation zone 370 to a biological regeneration reactor in whichmicro-organisms biologically degrade organics and certain inorganicsadsorbed on the adsorbent material.

In certain embodiments, the biological regeneration reactor 302 is anaerobic system, in which the micro-organisms are aerobic and thebiological regeneration reactor 302 is an aeration tank, including asource of oxygen (not shown), for instance, one or more diffusers, jetsuspension apparatus, or gas lift suspension systems, as described inPCT application number PCT/US10/38644, and the biological degradationincludes biological oxidation. The biology within the biologicalregeneration reactor is discussed in greater detail in PCT applicationnumber PCT/US10/38644, and in PCT Publication Number WO/09085252.

In additional embodiments, the biological regeneration reactor 302 is ananaerobic system, in which the micro-organisms are anaerobic.

Mixed liquor, including mixed liquor volatile suspended solids, isdischarged, through a separation subsystem 322 in or downstream of thebiological rector 302, and passed from an outlet 308 of the biologicalrector 302 to the membrane operating system 304 through an inlet 310.The membrane operating system 304 contains one or more membranes 340.Membrane-treated effluent 312 is discharged as permeate, and activatedsludge 314 as retentate is returned to the biological regenerationreactor 302. Optionally, activated sludge waste can be discharged fromthe return activated sludge line 314 via a waste line 318. In addition,an optional adsorbent material waste line 316 (as indicated by along-dash line) can remove spent adsorbent material that has lost itsefficacy, or be used to periodically remove adsorbent material, asdescribed in conjunction with FIG. 2 and in PCT Publication NumberWO/09085252 and in PCT application number PCT/US10/38644. Preferably,removed spent adsorbent material is replenished with equivalent amountsof fresh or regenerated adsorbent material. In additional optionalembodiments, all or a portion of membrane treated effluent 312 can bepassed via optional line 313 (as indicated by a long-dash line) to atertiary treatment zone 390 for final polishing.

The adsorbent material, such as granular activated carbon, and anyentrained liquid in stream 372 that passes into the biologicalregeneration reactor 302 is treated in a similar manner as the membranebiological reactor systems described in PCT application numberPCT/US10/38644 and in PCT Publication Number WO/09085252. However, theflux of stream 372 is relatively low. For instance, the flux of stream372 can be less than about 10%, 5%, 1%, 0.1% or even less than about0.001% of the flux of stream 351. In certain embodiments, the flux isthe minimum flow that can be passed through the membrane operatingsystem 304 without impacting the activity of the micro-organisms in thebiological regeneration reactor 302. Alternatively, this system can beoperated as a sequencing batch reactor, in which the effluent isdischarged when the wastewater has been adequately treated. In addition,in certain embodiments, the biological regeneration reactor 302 can bean aeration tank incorporating a combination of jet suspension or gaslift suspension, a quiescent zone and a wedge wire screen as isdescribed in PCT application number PCT/US10/38644. The membraneoperating system 304 in the low concentration wastewater treatmentsystem 354 of the present invention operates in a similar manner as themembrane biological reactors described in PCT application numberPCT/US10/38644 and in PCT Publication Number WO/09085252, however,operating at a very low flow rate. As biomass builds up in this system,it can be wasted in a manner similar to conventional membrane biologicalreactor systems, e.g., through a return activated sludge waste line 318.An adsorbent material waste line 316 is also provided. For instance, theadsorbent material can lose its adsorption capacity in conditions wherethe effluent subjected to upstream wastewater treatment containsinorganics or biologically inhibitory compounds that are not oxidizedeven with the substantially increased residence time using the lowconcentration wastewater treatment system of the present invention.Adsorbent material can be replaced in the system, e.g., using one ormore of the adsorbent material input locations described in PCTPublication Number WO/09085252, or in another suitable location, orsource 393.

On a continuous or intermittent basis, a side stream including adsorbentmaterial, and optionally mixed liquor to provide a liquid carrier forthe adsorbent material that facilitates transfer (e.g., in the form of aslurry), is removed from the biological regeneration reactor 302 andpassed to shearing zone 386. In the shearing zone 386, excess biomass issheared from the outer surfaces of the adsorbent material, such that theadsorption capacity of the adsorbent material in mixing zone 360 and/orthe adsorbent material settling and liquid separation zone 370 ismaximized. The shearing zone 386 can include one or more of a pump, ajet nozzle, an aerated grit chamber, a mechanical mixer, centrifugaldevices such as a hydrocyclone or centrifuge, or other apparatus thatfacilitates collision to effectuate shearing and in certain embodimentspromote separation of biomass from adsorbent material. The turbulence,inter-granule collisions, and collisions with other solid objects(stationary or moving) of the shearing zone and in certain embodiments,piping between the shearing zone and the biological regeneration reactor302, can result in shearing of excess biomass from the outer surface ofthe adsorbent material and become free floating mixed liquor suspendedsolids including mixed liquor volatile suspended solids.

In addition, the action of the fluid circulation, including highvelocity liquid and/or gas contacting surfaces of the adsorbent materialhaving excess biomass contributes to the desired shearing.

In certain embodiments, the adsorbent material shearing zone 386 cancomprise continuous regenerating system, for instance, having theconfiguration of a walnut shell filter or other similar unit operation,e.g., without the walnut shell media, for instance, of the type that iscommercially available from Siemens Water Technologies. For instance, asthe adsorbent material is passed through the continuous regeneratingsystem such as a continuous backwash filter or a walnut shell filter,inter-granule collisions and collisions with other solid objects and/orsurfaces in the continuous regenerating system causes shearing of excessbiomass from the granules of adsorbent material.

The slurry including sheared adsorbent material, free biomass shearedfrom the adsorbent material, and any mixed liquor is passed to anadsorbent material/biomass separation zone 387 to separate mixed liquorsuspended solids biomass sheared from the adsorbent material from themore dense adsorbent material. The adsorbent material/biomass separationzone 387 can include one or more of a hydrocyclone separator, acentrifuge, a side stream off of the continuous regenerating system, orother device suitable to separate adsorbent material from the biomass.

Note that in certain embodiments in which the biological regenerationreactor 302 includes jet nozzles or other apparatus that effectuatesshearing within the biological regeneration reactor 302 as described inPCT application number PCT/US10/38644, shearing zone 386 can beeliminated or bypassed, whereby a side stream from the biologicalregeneration reactor 302 is passed directly to the adsorption/biomassseparation zone 387.

The separated adsorbent material from the adsorbent material/biomassseparation zone 387 is passed to the mixing zone 360 via a line 389. Theadsorbent material returned to the mixing zone 360 contains a reducedconcentration of micro-organisms, and thus the organics in the lowconcentration wastewater can be adsorbed and exposed to the desiredbiology in the mixing zone 360 and in the adsorbent material settlingand liquid separation zone 370, prior to passage into the biologicalregeneration reactor 302.

Sheared biomass, which can include mixed liquid having mixed liquorsuspended solids and mixed liquor volatile suspended solids, from theadsorbent material/biomass separation zone 387, is passed to thebiological regeneration reactor 302 via a line 388.

In alternative embodiments, mixed liquor from the adsorbentmaterial/biomass separation zone 387 can be transferred downstream fromthe separation subsystem 322 of the biological regeneration reactor 302,for instance, combined with effluent 308, or passed directly into themembrane operating system. Notably, the separation requirements ofseparation subsystem 322 can be reduced or obviated in this alternativeembodiment, as mixed liquor can be transferred without the need forfurther separation. In certain embodiments, a source of mixed liquor forthe membrane operating system 304 (or clarifier/settling tank 395described in connection with FIG. 3) can be the liquid effluent from theadsorbent material/biomass separation zone 387.

In certain preferred embodiments, in order to facilitate settling of theadsorbent material in the adsorbent material settling and liquidseparation zone 370, granular activated carbon having relatively highspecific gravity levels is employed. For instance, granular activatedcarbon having a specific gravity greater than 1.10 can be used. Infurther embodiments, granular activated carbon having a specific gravitygreater than 1.40 can be used. Since the flow rate of the mixturecontaining granular activated carbon is relatively low, and thebiological regeneration reactor 302 and membrane operating system 304are relatively small, the higher energy requirements to maintain thedenser adsorbent material in suspension for a period of time sufficientto cause the desired level of biology within the biological regenerationreactor 302 are not a significant factor in the overall energyrequirements of operating the system.

Certain low concentration wastewater influents can include inorganiccompounds not capable of being degraded by the microorganisms. Thelevels of these inorganics must typically be reduced to within mandatedregulatory requirements. The adsorbent material can be modified with atreatment process and/or species thereby providing an affinity tocertain chemical species and/or metals in the wastewater, for instance,by impregnating suitable compounds, as further described in PCTapplication number PCT/US10/38644. As the micro-organisms in the lowconcentration wastewater treatment system of the present inventioncannot remove these inorganic compounds as effectively as they canremove organic compounds, systems using adsorbent material to adsorbinorganic contaminants generally require more frequent replacement ofadsorbent material as compared to systems treating only organiccompounds. The spent adsorbent material is removed from the system as itapproaches the adsorption limit for each compound to be removed from thelow concentration wastewater. For instance, sampling and analysis oronline monitoring can be performed periodically or continuously todetermine the organic or inorganic concentration from the lowconcentration wastewater treatment system of the present invention, asthe adsorption capacity of granular activated carbon for variouscompounds is inversely related to the waste concentrations in effluent371.

In an additional embodiment in which a tertiary treatment system 390 isemployed and includes a conventional adsorbent material filtrationsystem, contaminated adsorbent material from system 390 can beregenerated and/or reactivated using the adsorbent material biologicalregeneration reactor system 399, as indicated by line 394 between thetertiary treatment system 390 and the biological regeneration reactor302. Certain existing granular activated carbon adsorbent filter systemsuse staged adsorption, in which fresh granular activated carbon is addedin the final downstream filter, and the partially loaded granularactivated carbon is used in the upstream filter(s). In embodiments ofthe present invention in which contaminated adsorbent material fromsystem 390 is regenerated and/or reactivated using the adsorbentmaterial biological regeneration reactor system 399, the partiallyloaded granular activated carbon is transferred to the biologicalregeneration reactor 302 for regeneration and reuse as all or a portionof the adsorbent material in the mixing zone 360. Although line 394 isshown as transferring partially loaded adsorbent material directly tothe biological regeneration reactor 302, one of ordinary skill in theart, having the benefit of the teachings herein, will appreciate thatthis partially loaded adsorbent material can be introduced in theadsorbent material shearing zone 386, the adsorbent material/biomassseparation zone 387, the source 393 of adsorbent material, the mixingzone 360, or the liquid separation zone 370.

In some embodiments, one or more sensors can be included at locationsthroughout the system 350, including within the high flux adsorbentmaterial treatment system 359 and the low flux adsorbent materialbiological regeneration reactor system 399. These sensors can beemployed with a manually controlled and operated system or an automatedcontrol system to implement a suitable process modification in aprogrammable logic controlled wastewater treatment system. In oneembodiment, system 350 (or the high flux adsorbent material treatmentsystem 359 and the low flux adsorbent material biological regenerationreactor system 399) includes a controller 305 which can be any suitableprogrammed or dedicated computer system, PLC, or distributed controlsystem. The concentration of certain organic and/or inorganic compoundscan be monitored and measured by a sensor or sensors in fluidcommunication with effluent 312 or the effluent from outlet 308 of thebiological regeneration reactor 302, as indicated by dash-dot lineconnections between the controller 305 and both the effluent line 312and the intermediate effluent line between outlet 308 and inlet 310. Inanother embodiment, the concentration of volatile organic compounds orother property or characteristic of the system can be measured at one ormore of inlets 301, 351, or 310. In additional embodiments,concentration of certain organic and/or inorganic compounds can bemonitored and measured by a sensor or sensors in fluid communicationwith effluent 371 of the adsorbent material settling and liquidseparation zone 370, as indicated by dash-dot line connections betweenthe controller 305 and the effluent line 371. Sensors known to those ofordinary skill in the art of process control apparatus can include thosebased on laser-induced fluorescence or any other sensor suitable for insitu real time monitoring of the concentration of organic or inorganiccompounds in the effluent or other property or characteristic of thesystem. Sensors that can be used include submersible sensors for use inoil-in-water measurement which use UV fluorescence for detection, suchas enviroFlu-HC sensors available from TriOS Optical Sensors (Oldenburg,Germany). The sensors can comprise lenses which are coated or otherwisetreated to prevent or limit the amount of fouling or film that occurs onthe lenses. When one or more sensors in the system generate a signalthat the concentration of one or more organic and/or inorganic compoundsexceeds a predetermined concentration, the control system can implementa responsive action such as a suitable feedback action or feedforwardaction, including but not limited to removing adsorbent material viawaste discharge port 316 (as indicated by dotted line connectionsbetween the controller 305 and the valve associated with the wastedischarge port 316); removing return activated sludge via a waste line318 (as indicated by dotted line connections between the controller 305and the valve associated with the waste discharge port 318); adding newor regenerated adsorbent material via adsorbent material source 393 orat one of the other locations (as indicated by dotted line connectionsbetween the controller 305 and the valve associated with the adsorbentmaterial source 393); adding a different type of adsorbent material;modifying the hydraulic retention time; modifying the biologicalcharacteristics such as simple carbon food for micro-organisms or addingphosphorus, nitrogen and/or pH adjustment chemicals; and/or othermodifications as described above or that will be apparent to those ofordinary skill in the art.

In additional embodiments, the condition of the slurry containingadsorbent material can be characterized by one or more sensors(indicated in FIG. 3 with a shaded circle), such as optical sensorsand/or UV fluorescence sensors. For instance, one or more sensors can beassociated with the adsorbent material effluent stream 372, as indicatedby dash-dot line connections between the controller 305 and the stream372, to measure the concentration of one or more compounds in the streamand/or to determine the quality of the adsorbent material in the slurry.Further, one or more sensors can be associated with the adsorbentmaterial effluent stream from the biological regeneration reactor, asindicated by dash-dot line connections between the controller 305 andthe line between the biological regeneration reactor and the adsorbentmaterial shearing zone 386, and/or one or more sensors can be associatedwith the adsorbent material recycle line 389, as indicated by dash-dotline connections between the controller 305 and the recycle line 389. Inthe event that it is determined, based on information from one or moreof these sensors and/or other sensors or source of information, that theadsorbent material has a reduced adsorptive capacity, appropriatefeedback or feedforward action can be actioned.

Referring now to FIG. 4, a low concentration wastewater treatment system454 similar to system 354 shown in FIG. 3 is schematically illustrated.In system 454, an adsorbent material settling and liquid separation zone470 is provided, which can be one or more centrifuges, hydrocyclones,clarifiers, filters of various types, or other suitable separationdevices. The adsorbent material settling and liquid separation zone 470separates the liquid from the mixed stream 461, containing lowconcentration wastewater and adsorbent material from the mixing zone460.

In certain embodiments of the system 454, flow rates within the highflux adsorbent material system 459 are controlled to provide sufficientresidence time to allow the requisite level of contaminants from thestream 451 to adsorb onto the adsorbent material such as granularactivated carbon, and discharge a stream 471 meeting mandated qualitylevels for effluent discharge, or at levels of contaminationsufficiently low to be conveniently treated in a supplemental tertiarytreatment system 490. Other aspects of the low concentration wastewatertreatment system 454 are substantially the same as those described withrespect to system 354, and similar reference numbers are used in FIG. 4to represent similar or equivalent components.

Referring now to FIG. 5, a low concentration wastewater treatment system554 is schematically illustrated similar to system 454 shown in FIG. 4,wherein a low flux adsorbent material biological regeneration reactorregeneration system 599 includes a biological reactor system other thana membrane operating system. In particular, the low flux adsorbentmaterial biological regeneration reactor system 599 includes abiological regeneration reactor 502, an adsorbent material shearing zone586, adsorbent material/biomass separation zone 587, and aclarifier/settling apparatus 595 as a solids separation apparatus. Theclarifier/settling apparatus 595 can be either a clarifier apparatus, asettling apparatus, or an apparatus that performs both clarification andsettling. The system operates in a manner similar to system 354, butwithout the membrane operating system 304. Rather, to remove biomass andany other solids in the mixed liquor, a clarifier/settling apparatus 595is used. In particular, clarifier/settling apparatus 595 allowsactivated sludge to settle, and it is returned to the biological rector502 via a return activated sludge line 514. Clarified liquid is passedas effluent 512. The clarifier/settling tank 595 can be substituted inany of the systems described with reference to FIGS. 3, 4 and/or 6.Other aspects of the low concentration wastewater treatment system 554are substantially the same as those described in connection with system354, and similar reference numbers are used in FIG. 5 to representsimilar or equivalent components.

Referring now to FIG. 6, a low concentration wastewater treatment system654 is schematically illustrated that is similar to system 354 shown inFIG. 3, in which a high flux adsorbent material system 659 is anintegrated mixing/settling unit operation. For instance, in certainembodiments, the high flux adsorbent material system 659 can include acontinuous backwash filter or a continuous regenerating filtrationsystem similar to a continuous regenerating walnut shell filter (withoutthe walnut shell media), for instance, of the type that is commerciallyavailable from Siemens Water Technologies. Adsorbent material is removedas effluent 672, and the effluent 671 is wastewater that has hadcontaminants adsorbed therefrom. In certain embodiments, the continuousregenerating system also can perform stripping functions, in combinationwith, or as an alternative to, an adsorbent material shearing zone 686,and adsorbent material/biomass separation zone 687. Note that in suchembodiments, an adsorbent material/biomass separation zone is provideddownstream from the continuous backwash high flux adsorbent materialsystem 659. In an additional embodiment, high flux adsorbent materialsystem 659 includes an adsorbent material filtration apparatus such as aconventional tertiary carbon filter, in which treated water isdischarged as stream 671, and the partially loaded adsorbent material672, instead of being treated with conventional hot air or steamregeneration, for instance, is regenerated using the system 699 forbiologically treating adsorbed contaminants, which operates in a mannersimilar to that described with respect to FIG. 3, and regeneratedadsorbent material 688 is introduced into the tertiary carbon filterincluded in the high flux adsorbent material system 659. Other aspectsof the low concentration wastewater treatment system 654 aresubstantially the same as those described in connection with system 354,and similar reference numbers are used in FIG. 6 to represent similar orequivalent components.

In additional embodiments of the present invention, the source ofwastewater treated by the a high flux adsorbent material treatmentsystem integrated with a low flux adsorbent material biologicalregeneration reactor according to the present invention can be from asystem that treats primary solids including a portion of the BOD₅compounds by irradiation. In particular, and referring to FIG. 7, asystem 700 is shown for treating an influent wastewater stream 701containing suspended organic solids, dissolved organic solids, andoptionally, other contaminates such as inorganics. The influentwastewater stream 701 is introduced into a primary separation system753, such as a settling zone that allows biological solids to settle, aclarifier, a centrifuge, filter, screen, belt press, vortex separators,flotation devices, or other solids removal systems. In the primaryseparation system 753, solids and a portion of the easy to degradebiological oxygen demand compounds (BOD₅) materials are separated fromthe wastewater stream.

A typical primary treatment system is usually capable of reducing theBOD₅ concentration by about 40% to about 50%, and reducing the totalsuspended solids concentration by about 60% to about 70%. The solidsremoved in this step are usually the larger more slowly biodegradablesuspended solids and the effluent is typically a mixture of the morevolatile, easier-to-treat compounds present in the sanitary wastewater.Additional unit operations can also be used to provide a greater removalefficiency of the undissolved contaminants in the raw wastewater. Forinstance, one or more centrifuge devices, settling devices, orfloatation devices (e.g., dissolved air, induced air flotation) can beused. In further embodiments, additional unit operations can includeaddition of appropriate chemical compounds to treat to remove at least aportion of the less dense solids present in the raw wastewater.

In certain embodiments, a water phase, typically including dissolvedcontaminants and a minority portion of suspended solids, can bedischarged as a wastewater effluent containing some level ofbiologically labile compounds or a low concentration wastewater effluent751, and then treated downstream by a wastewater treatment system 754,which operates, for example, in a manner similar to one or more ofsystems 354, 454, 554 or 654 described previously. An effluent 712 isdischarged that is generally suitable for recycling as process water,irrigation, or environmentally friendly discharge. Untreated biologicalsolids are separated from the primary treatment system 753 as a solideffluent stream 774, typically containing entrained liquids, and arepassed, e.g., using a sewage trash pump or progressive cavity pump (notshown) suitable for handling of solid-laden liquids and slurries to ahomogenization zone 775, in which the solids are homogenized by asuitable mechanical apparatus such as one or more grinders and/orshredders. The homogenization zone 775 ensures that no compact lumps ofsolids are introduced into the downstream irradiation/disinfection zone777, thereby ensuring a maximum level of disinfection.

The untreated homogenized solids 776, generally in a slurry form, arepumped to an irradiation/disinfection zone 777, in which the solids aredisinfected using beta-ray, gamma-ray, x-ray or electron beam radiation,for instance, to achieve United States Environmental Protection AgencyClass A or B bio-solid disinfection requirements, or mandated sludgedisinfection requirements of other jurisdictions. The disinfected solids778 can thus be disposed of in an environmentally friendly manner.

FIG. 8 shows another embodiment of a wastewater treatment systemincluding irradiation of primary solids that are mixed with an inertmaterial to allow it to be reused as a soil substitute or for otheruses. In particular, a system 800 is similar to system 700, with theadditional operation of a mixing zone 763, in which disinfected solids778 are mixed with an inert filler material 762, such as sand, clay,and/or another suitable filler material, to produce a product 764, whichcan be useful as soil, compost, or fertilizer. The system 800 includingproviding the product 764 is particularly desirable for treatingwastewater having solids not having toxic organic or inorganiccompounds.

Optionally, a dewatering zone can be provided in the system 700 or 800.However, in system 800, excess water can be absorbed by sand or otherinert material mixed with the disinfected primary solids.

In certain embodiments, the influent wastewater 701 includes a highconcentration of metals, other inorganics, or toxic organics.Accordingly, even when disinfected to suitable levels, a mixture of thedisinfected bio-solids and filler material is not amenable as a soil,compost or fertilizer product. However, substantial capital cost, energyand size benefits can be attained, even in embodiments in whichdisinfected materials are disposed of in landfills, for instance, afterdrying and/or mixing with a suitable inert material.

In certain embodiments of the present invention, a system is configuredas a portable system, e.g., mounted on a skid, truck body, trailer, orthe like. Portability allows the tertiary treatment system to bemanufactured and delivered as a turnkey system. A portable orskid-mounted system will also facilitate the provision of the tertiarysystem on an as-needed basis, for instance, in situations in which othertertiary treatment systems are in service, under repair or beingconstructed. Further, certain facilities that are processing chemicalsfor a short period of time and create a particularly hard-to-treatwastewater stream can benefit from a portable or skid-mounted systemaccording to the present invention. Pipe fittings can be provided thatare adapted for mating with standard fittings and ports in existingwastewater treatment plants for ease and rapid installation of thesystem of the invention.

The system and method of the present invention avoids the problems ofthe prior art related to treating low concentration wastewater bypassing wastewater that has already been subjected to secondarytreatment, e.g., effluent from a secondary system, through an adsorbentmaterial mixing zone, wherein adsorbent material and secondary effluentare intimately mixed. Note that the secondary effluent, at the point ofpassage to the adsorbent material mixing zone, has had substantially allsolids and thus the majority of the high BOD₅ components removed. Thus,the secondary effluent is not amenable to biological oxidation from atraditional treatment biological system as the wastewater is too low instrength, contains biologically refractory compounds, containsbiologically inhibitory compounds, contains inorganic compounds, or acombination of these, which either cannot be oxidized biologically, orrequires a much longer residence time than is typically available tobiological oxidation. Typically a more energy intensive tertiary systemsuch as granular activated carbon adsorption filters or another tertiarytreatment system is used to polish this stream that is no longertreatable by a normal biological oxidation.

The low concentration wastewater treatment system of the presentinvention allows the contaminants to concentrate onto the carbon andprovides for treatment of low strength wastewater or a wastewater withbiologically-difficult to treat compounds, including bio-inhibitoryand/or biologically refractory compounds. In addition, inorganiccompounds present in the low concentration wastewater can be adsorbed.

The low concentration wastewater treatment system of the presentinvention is a lower cost alternative to the methods currently beingused as it utilizes biological oxidation—typically the lowest costremoval technology available for treating wastewater. Activated carbonadsorption columns are typically very expensive to operate and require avery energy intensive process to regenerate carbon, typically based onincineration to regenerate the granular activated carbon. Deployment ofthe tertiary treatment system of the present invention as a replacementor a supplement to an activated carbon column can produce a considerableenergy savings. As a result, carbon credits for carbon dioxide reductionassociated with the decreased energy consumption can be earned.

Volumetric capacity requirements for the various operations within thelow concentration wastewater treatment system of the present inventioncan be significantly less than a conventional membrane biologicalreactor used to treat the same volume of wastewater and is significantlysmaller than a conventional sewage treatment system not utilizingmembranes.

The use of the low concentration wastewater treatment system of thepresent invention allows for treatment of a relatively low strengthwastewater, essentially only the dissolved contaminants and a smallamount of entrained solids in the wastewater, and still results in aneffluent having very low concentrations of hard-to-treat (refractorycompounds) or simple organic compounds that were originally present inthe wastewater. It is noted that certain preferred embodiments aredescribed in conjunction with treatment of low concentration wastewater,and are referred to as “low concentration wastewater treatment systems.”Nonetheless, as will be appreciated by one having ordinary skill in theart, having the benefit of the present disclosure, the wastewatertreatment system of the present invention can advantageously be employedto treat wastewater having some level of biologically labile compoundsas well as compounds entirely resistant to bio-decomposition,biologically inhibitory compounds, and/or biologically refractorycompounds, or a combination of these. For instance, dissolventbiologically labile compounds can be adsorbed on the adsorbent materialalong with compounds entirely resistant to bio-decomposition,biologically inhibitory compounds, and/or biologically refractorycompounds, or a combination of these, and passed to the adsorbentmaterial biological regeneration reactor system described herein. Thebiologically labile compounds can serve as food alone or in combinationwith a secondary nutrient source to support the micro-organisms.

Useful adsorbent materials for the present invention include varioustypes of carbons, such as activated carbon. In particular, granularactivated carbons are very effective, since the size range and densitiesof the granules can be selected to enable their retention in apredetermined portion of the system and thereby substantially preventthem from fouling and/or abrading the membranes.

In systems in which the granular activated carbon is not subjected tosignificant shearing forces and/or inter-granule collision, the granularactivated carbon can be produced from wood, coconut, bagasse, sawdust,peat, pulp-mill waste, or other cellulose-based materials. One suitableexample is MeadWestvaco Nuchar® WV B having nominal mesh sizes of 14×35(based on the U.S. Standard Sieve Series).

In additional embodiments, particularly those in which shearing actionis provided by turbulence and/or inter-granule collisions in a pumpand/or jet nozzle, use of adsorbent material(s) having higher hardnessvalues are desirable. For instance, granular activated carbons derivedfrom bitumen or coal-based materials are effective. In a particularembodiment, the granular activated carbon is derived from lignite.

Carbon materials can also be provided which are modified with atreatment process and/or species thereby providing an affinity tocertain chemical species and/or metals in the wastewater. For instance,in wastewaters having a relatively high level of mercury, at least aportion of the adsorbent material preferably includes granular activatedcarbon impregnated with potassium iodide or sulfur. Other treatmentsand/or impregnated species can be provided to target specific metals,other inorganic compounds and/or organic compounds.

In addition, the adsorbent can be a material other than activatedcarbon. For instance, iron-based compounds or synthetic resins can beused as the adsorbent materials, alone or in combination with otheradsorbent materials, e.g., in combination with granular activatedcarbon. Further, treated adsorbent materials other than activated carbonthat target certain metals, other inorganic compounds or organiccompounds can be used. For instance, in wastewaters having relativelyhigh levels of iron and/or manganese, at least a portion of theadsorbent can comprise a granular manganese dioxide filtering media. Inwastewaters having arsenic, at least a portion of the adsorbent cancomprise granular iron oxide composites. In wastewaters including leador heavy metals, at least a portion of the adsorbent can includegranular alumino-silicate composites.

In one embodiment, the adsorbent material can be selected based upon adesired specific gravity range. In order to maintain the adsorbentmaterial in suspension within acceptable energy consumption/cost ranges,specific gravity ranges relatively close to that of the wastewater aredesirable. On the other hand, in embodiments in which separation isbased at least in part on rapid settling of the material, higherspecific gravities are more suitable. In general, the specific gravityis preferably greater than about 1.05 in water at 20° C. In certainembodiments, the specific gravity is greater than about 1.10 in water at20° C. A suitable upper limit for the specific gravity is, in certainembodiments, about 2.65 in water at 20° C.

Therefore, the adsorbent material having a specific gravity range isselected which provides sufficient suspension and therefore sufficientcontact with the wastewater and its contaminants. In addition, incertain embodiments, the specific gravity range provides sufficientsettling characteristics for subsequent removal of the adsorbentmaterial from the wastewater. In further embodiments, selection of thespecific gravity of the adsorbent material is based on minimization ofthe energy required to maintain the adsorbent material in suspension.

Furthermore, the desired adsorbent material, such as granular activatedcarbon, has a hardness level that minimizes creation of fines and otherparticulates due to inter-granule collisions and other process effects.

The size of the adsorbent material that the separation subsystem isdesigned to retain and thereby prevent its passage into the membraneoperating system is optimized to minimize the amount of adsorbentmaterial and fines entering the membrane operating system. Therefore, inembodiments in which the solids separation apparatus is a membraneoperating system, abrasion and fouling caused by carbon granules orother granular materials impinging on the membranes is minimized, whilestill providing the operational advantages associated with the use ofadsorbent materials including activated carbon.

Suitable granule sizes for the adsorbent material are selected tocomplement the selected screening/separation methods, and the needs ofthe particular wastewater being treated. In certain preferredembodiments, the bottom limit of effective granule size of the adsorbentmaterial is selected so that it can easily be separated from the flow ofmixed liquor entering the membrane operating system tank(s) in which themembranes are located. In general, the effective granule size of theadsorbent material has a bottom limit of about 0.3 millimeters, wheregreater than about 99.5 weight % of the adsorbent material is above thebottom limit; preferably having a lower limit of about 0.3 millimetersto an upper limit of about 2.4 millimeters (corresponding to a mesh size50 to a mesh size 8, based on United States Standard Sieve Series),where greater than 99.5 weight % of the adsorbent material is within thelower and upper limit; and in certain preferred embodiments about 0.3millimeters to about 1.4 millimeters (corresponding to a mesh size 50 toa mesh size 14, based on the United States Standard Sieve Series) wheregreater than about 99.5 weight % of the adsorbent material is within thelower and upper limit. It has been demonstrated that a granularactivated carbon with a minimum effective granule size of about 0.5millimeters to about 0.6 millimeters can be easily and efficientlyscreened from the mixed liquor with a suitable separation system, andsuch effective sizes, in granular activated carbon of suitabledensities, also can economically be maintained in suspension.

The use of adsorbent material to adsorb the compounds entirely resistantto bio-decomposition, biologically inhibitory compounds, and/orbiologically refractory compounds, or a combination of these, allows theprocess to handle a much higher flow rate of wastewater thanconventional systems, as the organisms that are biologically decomposingthe organic compounds would not be limited by the hydraulic residencetime of conventional systems. The biologically inhibitory compoundsand/or certain biologically refractory compounds remain on the adsorbentmaterial for an extended period of time, and thus the micro-organismshave many times the hydraulic residence time to break them down. Thisallows a significantly smaller unit to treat the wastewater stream thanwould be required without the addition of adsorbent material.

The use of the low concentration wastewater treatment system of thepresent invention rather than a conventional system or a conventionalsystem with addition of powdered activated carbon eliminates problemsassociated with settling of solids that would occur in a high flow rateconventional system that does not use a membrane for solids separationfrom the effluent.

The low concentration wastewater treatment system of the presentinvention can be modified to treat specific contaminants that might bepresent in any particular wastewater by using an adsorbent material thathas been specially treated to selectively adsorb the particularcontaminant of concern. For example, a granular activated carbon orother adsorbent material that has been specially treated to adsorbmetals can be used for wastewaters that have high concentrations ofmetals. The dissolved metals can preferentially adsorb onto the treatedgranular activated carbon and then be removed from the effluent. Aperiodic replacement of the adsorbent material allows the metals to beremoved from the system and maintain a desired level of adsorptivecapacity.

The invention provides a low cost alternative to permanent installationsof high cost activated carbon adsorption columns or any of a number ofother tertiary treatment systems that are expensive to operate. Inaddition, the present invention provides a simpler, smaller footprint,lower operating cost wastewater treatment system that can be set up andoperated in a very short period of time and if necessary, can beconfigured as a portable system/apparatus. It can be deployed forperiods of upset conditions or during events when a wastewater treatmentplant is required to treat wastes that it was not normally capable oftreating.

The system and method of the present invention avoids the treatment ofthe entire effluent stream in an expensive tertiary treatment system. Itadsorbs the contaminants from the low concentration wastewater andtreats them in a high flux adsorbent material treatment systemintegrated with a low flux adsorbent material biological regenerationreactor.

Previously developed tertiary systems attempt to treat the effluent fromexisting wastewater treatment plants having low concentrations ofcontaminants with an expensive activated carbon adsorption system orsome other expensive tertiary treatment system. In all of these, theentire wastewater stream is treated with the tertiary treatment method.The system and method of the present invention removes pollutants fromthe full wastewater stream by adsorption, and then treats the adsorbentmaterial in a low flux biological regeneration system that is relativelyinexpensive to operate.

The method and system of the present invention have been described aboveand in the attached drawings; however, modifications will be apparent tothose of ordinary skill in the art and the scope of protection for theinvention is to be defined by the claims that follow.

1. A method for treating wastewater that contains solids and biologicaloxygen demand compounds, the process comprising: separating a majorityof the solids and biological oxygen demand compounds from the wastewaterfeed using a primary separation process to provide a solids phase and awater phase including wastewater, the solids phase containing an initiallevel of pathogens; irradiating the solids phase to reduce the level ofpathogens; mixing the wastewater with adsorbent material in a mixingzone for a time sufficient for adsorption of contaminants from thewastewater onto the adsorbent material; separating and removing a majorportion of the wastewater from the mixture of wastewater and adsorbentmaterial; passing the adsorbent material having contaminants adsorbedthereon and a minor portion of the wastewater to a biologicalregeneration reactor; retaining the adsorbent material and wastewater insuspension in the biological regeneration reactor for a period of timethat is sufficient to allow microorganisms in the biologicalregeneration reactor to biologically act on at least a portion of theadsorbed contaminants; discharging biologically treated water effluentfrom the biological regeneration reactor; and recycling regeneratedadsorbent material to the mixing zone.
 2. The method of claim 1, furthercomprising homogenizing the separated solids phase prior to theirradiation.
 3. The method of claim 1, wherein the irradiating comprisesexposing the solids to one or more of beta-ray, gamma-ray, x-ray orelectron beam radiation.
 4. The method of claim 1, wherein the step ofseparating the solids and biological oxygen demand compounds from thewastewater feed produces low concentration wastewater.
 5. The method ofclaim 1, further comprising removing solids from the biologicalregeneration reactor water effluent using a membrane operating system, aclarifier and/or a settler.
 6. The method of claim 1, which furthercomprises shearing any accumulated biomass from the adsorbent materialprior to recycling to the mixing zone.
 7. The method of claim 6, furthercomprising separating the biomass from the adsorbent material prior torecycling the adsorbent material to the mixing zone.
 8. The method ofclaim 1, further comprising mixing the irradiated solids phase with afiller material to produce a soil, compost, or fertilizer product.